1. GENERAL INFORMATION
Acute myeloid leukaemia (AML) accounts for about 30% of all leukaemias in adults, and approximately 22,250 new cases are diagnosed in Europe each year (Curado 2007; Ferlay; 2007), aout 0.6% of all cancers. Overall, AML is marginally less common than chronic lymphoid leukaemia, the most common leukaemia in adults, but is five times more frequent under the age of 50 (Curad, 2007) (Figure 1).
The crude annual incidence rates among the European population ranged between 0.5 and 5.5 per 100,000. AML is more common in men then women, with a sex ratio of 2 to 1 (Curad 2007).
In the UK incidence has risen by about 70% in both sexes since 1971, while in the early 1990s reached a plateau(Coleman 2000; Rachet 2008). The rice in incidence was less steep among more deprived groups, leading to lower incidence than among more affluent groups of the population, particularly for men.
In Italy, during the period 1998-2002, AML is increasing over time among men, while it is stable among women(AIRTum report 2006).
Figure 1. Age specific incidence rates in England of different subtypes of leukemia
Leukaemias are usually fatal. In Europe, relative survival for adults diagnosed with AML during 2000-2002 was 15% at at five years, with no difference between men and women. In the US, for the same period 5-year survival was 14% (Verdecchia 2007). For AML the profile of 5-year and 10-year survival between 1991-93 and 2000-2002 were similar, although 10-year survival was lower, indicating that tendency for death to occur mainly within 5 years after diagnosis.
Five-year relative survival decreased markedly with age from 44% to 3% from the youngest (15-45 years) to the oldest age group of patients (75 years and over).
There are major between-country differences in survival for European patients with AML: some European countries like Slovenia were characterised by low 5-years relative survival (8%) while, the Northern European coutries such as Iceland and Sweden 5-year-survival were higher, 27% and 22 % respectively. Socio-economic inequalities in survival for patients with leukaemia have been reported. In England and Wales, the deprivation gap in survival for leukaemia in adults in consistently and significantly in favour of the more affluent groups (Rachet 2008).
1.3 Risk factors
Ionizing radiation, occupational exposure to benzene and smoke are associated with AML. The International Agency for Research on Cancer (IARC) has reported that there is sufficient evidence for causality between active smoking and adult AML ( IARC 2004). In the Canadian population the estimated risk (adjusted odd ratio) was 1.5 for heavy smokers, with a clear dose-response relationship (Kasim 2005). Exposure to radiation at sufficiently high doses has increased the risk of developing leukaemia by over fivefold. Excess numbers of cases of leukaemia also been observed among patients treated with X-rays or gamma-rays for malignant or benign diseases. Important evidence comes from studies of women in 15 countries who were irradiated for cervical cancer and persons who were irradiated for ankylosing spondylitis in the United Kingdom (IARC 2000).
Some antineoplastic drugs are leukeaemogenic. AML may occur in a small proportion of cancer patients treated with chlorambucil, cyclophosphamide, melphalan, thiotepa, treosulphan or etoposide, as well as certain combination of chemotherapy (Stewart 2003). Electricians, power line workers, and electronics and other workers thought to be exposed to non ionising electrical and magnetic fields have been reported to have an elevated leukaemia (primarily AML) risk in some but not all studies in which assessment of occupational exposure was based on job titles (Savitz 1987). A large study of Canadian and French utility workers demonstrated a small excess of AML (Theriault 1994). Benzene-exposed shoe, leather, rubber and chemical manufacturing workers have been repeatedly shown to have a 2 – 10 fold increased risk of leukaemia (primarily AML) (IARC 1981 ). There are recognised autosomal dominant and recessive cases of familial AML (Horwitz 1997; Song 1999) in addition to associations with a variety of genetic syndromes including trisomy 21 (Hasle 2000) and those characterised by defective DNA repair (eg Fanconi’s anaemia, ataxia telangiectasia and Bloom’s syndrome) (Taylor 2001). The syndrome of familial platelet disorder with a propensity to AML (FPD/AML) is associated with inheritance of RUNX1 mutation (Song 1999). CEBPA mutation has now been reported in one kindred affected by familial AML, primarily of M1 and M2Eo subtypes qv (Smith 2004).
2. PATHOLOGY AND BIOLOGY
2.1. Diagnostic Studies
2.1.1. Morphological classification
Light microscopy supplemented by cytochemistry is the first method for the diagnosis of AML and its further sub-classification. Examination of bone marrow and peripheral blood specimens stained with Wright Giemsa or May-Grunwald-Giemsa (MGG) stain provides a rapid initial and frequently conclusive diagnosis. Myeloblasts are characteristically large cells with a low nuclear-cytoplasmic ratio, a finely stippled nuclear chromatin pattern and often multiple prominent nucleoli. Cytoplasmic azurophilic granules are usually present with Auer rods visible in many cases. Such blasts are present in a background of other lineages appearing in varying proportion and degree of maturation. In some cases this can include mature eosinophils and basophils. Evidence of trilineage dysplasia is noted in 10 – 15% of de novo cases.
Acute promyelocytic leukemia (APL) is morphologically distinct in over 90% of cases. These cells are typically hypergranular with Auer rods present, often collected into bundles or ‘faggots’. One quarter of cases of APL appear as a microgranular variant. This should be suspected in cases with minimal granulation, bi-lobed nuclei with a folded configuration, monocytoid features and strong myeloperoxidase [MPO] staining.
For more than 25 years, the classification system for AML was based on the French American British (FAB) group criteria established in 1976. This classification was updated in 1985 and recommended a 500-cell count with accurate morphological and cytochemical quantitation of lineage commitment and differentiation14. A diagnosis of AML relied on the presence of more than 30% myeloid blasts in the bone marrow. More than 3% of blasts had to be positive on Sudan Black (SBB) or MPO staining with the exceptions of AML M0 and AML M7 (see below). In AML M6, the most striking feature was an erythroid predominance of ≥ 50% with at least 30% of the non-erythroid cells being blasts. There are several excellent publications on this subject15.
Table 1. FAB classification system for AML
|M0||AML with no differentiation*||3|
|M1||AML without maturation||15 – 20|
|M2||AML with granulocytic maturation||25 – 30|
Hypogranular variant APL
|5 – 10|
|M4||Acute Myelomonocytic leukemia||25 – 30|
Acute Monoblastic leukemia
Acute Monocytic leukemia
|2 – 10|
|M6||Erythroleukemia||3 – 5|
|M7||Megakaryoblastic leukemia *||3 – 12|
* typically diagnosed on Immunophenotyping
The progress in the biological characterization of AML led to an expert panel, working on behalf of the World Health Organisation (WHO), to establish an improved classification which identifies new entities with specific morphologic, cytogenetic and molecular features16-18. Compared to the FAB classification, the WHO has lowered the threshold between AML and MDS from 30% to 20% bone marrow blasts. This reflects that RAEB-t is biologically and prognostically related to AML rather than to MDS. Additional changes are the diagnosis of AML with less than 20% blasts, in the presence of one of the main 4 chromosomal translocations, and the addition of new categories reflecting the etiology of the leukemia either arising from a pre-existing dysplasia or as a consequence of exposure to chemotherapy. ‘Acute basophilic leukemia’ and ‘acute panmyelosis with myelofibrosis´ have also appeared as new categories within AML – unspecified19.
Table 2. WHO classification of AML
|AML with recurrent cytogenetic translocations||
AML with features of t(8;21)(q22;q22)
AML with features of t(15;17)(q22;q12)
AML with features of inv(16)(p13q22)
AML with 11q23 abnormalities
5 – 12
10 – 15
3 – 5
|AML with MDS related features||
AML with multilineage dysplasia
AML arising in previous MDS
10 – 15
|AML, therapy related||
Alkylating agent related
|5 – 10|
|Acute myeloid leukemia, unspecified||AML minimally differentiated [M0]
AML without maturation [M1]
AML with maturation [M2]
Acute myelomonocytic leukemia [M4]
Acute monocytic leukemia [M5]
Acute erythroid leukemia [M6]
Acute megakaryocytic leukemia [M7]
Acute basophilic leukemia
Acute panmyelosis with myelofibrosis
|40 – 50|
Cytochemistry is standard on a type C basis. All cases of AML, except M0 and M7, require MPO or SBB positivity. Positive reactions tend to be coarse and granular. MPO may be negative by light microscopy, or only showing up as a faint fine granularity. This is particularly the case in subtypes M0 or M5, M6 and M7 with minimal maturation or basophilic/mast cell leukemias. These cases would require immunophenotyping in order to detect cytoplasmic MPO positivity. However, M0 and M7 usually do not have MPO positivity but they have additional myeloid markers in absence of MO.
Other stains such as -naphthyl acetate esterase (ANAE or other non-specific esterase, NSE) can be used to identify a monocytic component. A NSE stain can be performed if AML-M2, M4 or M5 are suspected, but it is not necessary if immunphenotyping is performed. Monoblasts are diffusely positive, although punctate positivity is seen in megakaryoblasts and erythroblasts.
Chloroacetate esterase (CAE) staining is positive in the late myeloblast and early promyelocyte stage. CAE can be combined with ANAE in a ‘combined esterase’ test to identify separate granulocytic and monocytic components. The CAE should not replace either the MPO or SBB staining, as it is less sensitive, often being negative in early myeloblasts, and hence can be ommitted.
Acid phosphatase and PAS stains are also no longer necessary, however, a Perl’s iron stain may help in detecting dyserythropoietic ring sideroblasts and a toluidine blue stain may identify an abnormal basophil or mast cell component.
Immunophenotyping is essential if the blasts are not obviously myeloid or when cytochemistry is uninformative or equivocal. Options for analysis include flow cytometry or immunocytochemistry20. The latter however, is less reliable for cytoplasmic markers and is more subjective. All haemopoietic cells will express the common leucocyte antigen (CD45) and 40 – 60% of cases will express the stem cell marker CD34. Most cases express highly specific myeloid antigens such as CD117 (c-kit) and cytoplasmic myeloperoxidase (cMPO). Other myeloid antigens, such as CD33, CD15 and CD13, are less specific, and can occur in certain cases of acute lymphoblastic leukemia. As well as confirming the myeloid origin of the blasts, immunophenotyping can identify evidence of monocytic, erythroid, or megakaryocytic differentiation. Markers associated with lineage differentiation include CD14 and CD11b in AML-M4 and M5, glycophorin A in AML-M6 and platelet glycoproteins CD41, CD42 and CD61 in AML-M7.
Two consequences of the increased use of immunophenotyping have been the recognition of the category AML-M0 and of biphenotypic/bilineage leukemias.
In AML-M0 less than 3% of blasts are positive by MPO or SBB staining yet are confirmed to be myeloid by the demonstration of either myeloid antigen positivity with immunophenotyping. The ultraestructural expression of myeloperixidase can be studied using electron microscopy, although this is not routinely done.
Biphenotypic leukemias express both lymphoid and myeloid antigens and there exist well-validated scoring systems for the recognition of these leukemias. Distinction should be made between these entities and lymphoid antigen positive AML (Ly+ AML), as expression of other less specific lymphoid antigens is a recognised feature in approximately 20 – 30% of cases of AML. CD7 is most commonly expressed (approximately 20% of cases) although CD19, CD2, CD20 or CD10 may be (see Table 3).
Immunocytochemistry may sometimes be used to diagnose genetic translocations, for example, anti-PML monoclonal antibodies will show a microspeckled distribution in the presence of a PML-RAR fusion protein rather than obvious nuclear bodies seen with wild-type PML. Immunohistochemical study in trephine biopsy using antibodies detecting nucleophosmin (NPM1) allows to identify cases with abnormal cytoplasmic localization, which reflects mutations in the C-terminus of the protein21,22.
In addition to the diagnostic purposes immunophenotyping is used to identify leukemia-associated aberrant immunophenotypes (LAIPs) based on which minimal residual disease can be monitored flow cytometrically during the course of the disease20,23,24.
Table 3. EGIL criteria
CD3 cyt or sur
*Citochemistry or immunology; cyt: cytoplasmatic; sur: surface
Cytogenetic evaluation is recommended on a type C basis in all cases of acute leukemia. Metaphase G banding can detect the majority of chromosomal abnormalities and karyotypic changes, both numerical and structural, that occur in 50 – 70% of adults with AML25. Trisomy 8 is the most common numerical cytogenetic abnormality seen. Certain structural chromosomal translocations are recognised to have characteristic morphological features, a few are listed:
t(8;21)(q22;q22) translocation – 90% of cases are classified as AML-M226. This entity is associated with characteristic prominent Auer rods, marrow eosinophilia, salmon-coloured cytoplasmic granules in early myeloid cells, large cytoplasmic vacuoles, CD19 and CD79a positivities and strong MPO staining. Other associations are high CD34 positivity, CD56 expression, low CD33 expression and loss of the Y chromosome in men.
t(15;17)(q22;q12)which is seen in the majority of cases of AML-M3 and M3-variant.
inv(16)(p13q22) or t(16;16)(p13;q22) – 90% are classified as AML-M4Eo. T-lineage CD2 positivity is frequent.
abnormalities of 11q23 – typically have monocytic or myelomonocytic morphology and are often seen in infant and congenital leukemias or podophyllotoxin-related leukemias. t(9;11)(p21;q23) and t(11;19)(q23;p13.3) are the most commonly seen translocations at this site.
t(6;9)(p23;q34) – M1 or M4 morphology with marrow basophilia.
Abnormalities of 3q21q26 – M1 morphology with trilineage dysplasia and peripheral thrombocytosis27.
t(8;16)(p11;p13) – M4 or M5 AML with erythrophagocytosis28.
2.1.5. Molecular analysis
Reciprocal translocations can be detected by PCR-based techniques. Genetic targets for these include RUNX1(CBFα2)-ETO [t(8;21)], CBFß-MYH11 [inv(16)] and PML-RARα [t(15;17)]. There are also exceptions where APL is seen with t(11;17)(q23;q21) [PLZF/RARα], t(11;17)(q13;q21) [NuMA/RARα] or t(5;17)(q32;q12) [NPM/RARα]29.
Occasionally molecular techniques highlight discordance between standard cytogenetic analysis, FISH and PCR-based methods. This may reflect the presence of cryptic translocations30,31, and suggests a need to screen samples by molecular analysis when morphology is suggestive of a translocation despite normal cytogenetics and FISH32. For example, PCR remains the gold standard for the diagnosis of APL. Only approximately 80% of patients with molecular evidence of the PML/RARα fusion have a detectable t(15;17) on G-banding. This may be due to either failure to obtain metaphase cells or cryptic translocations with insertion of RARα into PML. Inv(16) can often be a subtle rearrangement on G-banding and may be missed. Therefore, if it is suspected, eg. M4Eo morphology, one should consider FISH or RT-PCR analysis for exclusion of a CBFß-MYH11 rearrangement. Unfortunately, not all translocations have easily recognizable morphology and some translocations, such as 11q23 abnormalities affecting the MLL gene, have many partner genes that would necessitate multiplex PCR33.
There is an increasing body of work looking at the presence of mutations, deletions and overexpression affecting genes involved in myelopoiesis in the context of AML. Such genes include N- and K-RAS34, FLT335, KIT36, CEBPA37,38. PTPN1139, PU.140, NPM121, RUNX141, WT142, BAALC43, ERG44, and EVI145, among others. The ‘Gilliland hypothesis’ for AML development supports the need of at least two classes of molecular events leading to excessive proliferation and impaired cell maturation, respectively46. DNA and RNA screening for molecular alterations is of increasing interest, since many of them have significant prognostic impact and allow identifying potential therapeutic targets. Among the molecular alterations, one of the most frequent is the internal tandem duplication of the FLT3 gene which associates to increased relapse rate and decreased survival47-49. KIT gene mutations are less common and lead to poor prognosis in patients with t(8;21) or inv16 AML50,51. EVI1 or ETS related gene (ERG) overexpression confer adverse outcome44. In contrast, NPM1 mutation in the absence of FLT3 abnormalities52 and CEBPA mutation53, have been identified as favorable prognostic factors. To detect these molecular alterations is particularly relevant in AML with a normal karyotype, since this group includes patients with a heterogenous outcome54.
Work is underway using a genomic approach to AML genetics including 24 colour FISH, spectral karyotyping and M-FISH or CGH arrays55. These studies have the potential to identify multiple small insertions and deletions throughout the genome. Gene expression analysis using either cDNA or oligonucleotide array technology has been shown to separate AML from acute lymphoblastic leukemia (ALL) and to separate the common translocations from each other56,57. Their use, however, remains investigational. Such work is continuing to expand however and offers potential in identifying novel expression patterns, mutation specific signatures and teasing out prognostically different groups within a previously homogeneous group58,59. The reproducibility of the microarray technology led to the initiation of prospective studies aiming at the validation of gene expression profiling as a diagnostic tool in AML60,61.
2.2. Differential diagnosis
Alternative diagnoses for AML include MDS, ALL, bi-phenotypic acute leukemia, myeloid blast phase of chronic myeloid leukemia, transformed myelofibrosis, secondary metastases eg. alveolar rhabdomyosarcoma/neuroblastoma or even gross megaloblastic anaemia (masquerading as AML-M6).
Once a haematological malignancy has been confirmed, using CD45 expression if necessary, it is then essential to differentiate AML from ALL, rare bi-lineage and bi-phenotypic leukemias62 and MDS. Conventional morphology supplemented by cytochemistry is often sufficient for this purpose identifying the presence of granulation, Auer rods and myeloid maturation. Occasionally myeloblasts can have typical agranular L2 lymphoblast morphology and may present some diagnostic confusion. These cases are typically M0, M1, M6 or M7 and their myeloid nature can be demonstrated either by immunological markers or, in cases of M7, by ultrastructural demonstration of platelet peroxidase. It is therefore recommended on a type C basis that all acute leukemias with lymphoblast morphology should be examined immunologically using a standard primary panel of antibodies to confirm their myeloid nature and to exclude ALL by demonstrating negativity for lymphoid markers63. Biphenotypic leukemias will be identified by the careful application of primary antibody panels, supplemented with secondary panels as necessary, according to established guidelines64. Scoring systems (EGIL criteria; see Table 3) exist to differentiate biphenotypic leukemias from AML expressing aberrant lymphoid antigens (Ly + AML)65.
It is important to emphasize that diagnostic cut-offs between categories in existing classification systems are inevitably arbitrary. The need for therapy should therefore be decided in light of the patient’s condition as well as their marrow morphology.
3.1. Physical and Laboratory
3.1.1. Clinical presentation
Symptoms present at diagnosis typically result from the increasing burden of leukaemic cells, their effects on bone marrow function and their infiltration of other tissues. Most patients experience weakness and fatigue66. Bone marrow failure may present with the symptoms of anaemia such as fatigue, exertional dyspnoea, palpitations, angina or claudication. Thrombocytopenia is usually manifest as epistaxis, gingival haemorrhage, menorrhagia, cutaneous petechiae or occasionally significant gastrointestinal, urinary or intracranial haemorrhage. Neutropenia predisposes the patient to infection. These are typically bacterial or fungal in nature and common sites for sepsis include the teeth and oropharynx, sinuses, lung, skin, perineum and bowel. Fever is a presenting feature in 15 – 20% of patients. In those patients who present with a blast count > 50 x 109/l there may be features of hyperviscosity due to leucostasis, such as dyspnoea, hypoxia, respiratory failure, headache, seizures, confusion, coma visual disturbances or priapism. Organomegaly and adenopathy are present in up to one half of patients. Leukaemic infiltration may also involve the central nervous system [CNS] adults. This is usually manifest as leptomeningeal disease with headache and isolated cranial nerve palsies (especially V and VII), however intracranial masses can occur – usually in the setting of M4Eo with inv(16). Leukaemic infiltration of the skin (leukemia cutis) occurs in about 10% of cases and gingival infiltration can also be seen – typically in the monocytic leukemias, AML-M4 and M5. Other organs can be involved, such as the testes, but this is rare. In some patients extramedullary accumulation of myeloblasts (‘chloroma’, ‘granulocytic sarcoma’) can be identified67. These are characteristically found in the orbit, sinuses, skin or bone although may occur in other tissues, like the gastro-intestinal tract..
3.1.2. Laboratory findings
At diagnosis most patients are anaemic and neutropenic. A peripheral blood leucocytosis is present in over 50% of cases, although a white count greater than 100 x 109/l is only seen in 20% and usually occurs in the context of AML-M4 or M5. Aleukemic leukemia, where blasts are absent in the peripheral blood, is rare. At diagnosis the bone marrow is infiltrated with between 20 and 100% myeloblasts. Renal function may be impaired secondary to renal infiltration or hyperuricaemia and abnormalities of liver function may also reflect leukaemic infiltration. Disseminated intravascular coagulation (DIC) is common in varying degrees of severity and is especially, although not exclusively, associated with APL. Serum lysozyme concentration may be raised in cases of AML M4 or M5, with hypokalaemia from resultant renal tubular dysfunction. LDH levels may also be elevated in some cases.
3.2. Pathological diagnosis
3.2.1. Appropriate diagnostic sampling
A bone marrow aspirate is the standard method for obtaining diagnostic samples. It is important that the resultant smear or crush preparation is well spread and well stained. A trephine biopsy should be performed in the event of a ‘dry tap’ or a haemodilute or aparticulate sample. These poor quality samples are especially common in cases of AML M7 due to heavy bone marrow fibrosis or APL when the marrow often clots before spreading. It should be noted that a trephine imprint (‘trephine roll’) can provide useful information on marrow cellularity and can be treated as an aspirate smear for morphological and cytochemical examination. Immunohistochemistry is also possible on sections of the trephine biopsy after fixation68. Trephine biopsy is therefore recommended on a type C basis when the aspirate quality is poor and is essential in order to distinguish hypoplastic AML from either hypoplastic MDS or aplastic anaemia.
Peripheral blood can be used as an alternative to marrow for immunophenotyping and cytogenetic studies providing that there are significant numbers of circulating blasts. Early examination of the cerebrospinal fluid [CSF] is mandatory for patients with clinical signs or symptoms of CNS disease and is suggested for those at increased risk of CNS involvement i.e. those with a high presenting count or subtypes AML-M4 or M5. Lumbar puncture should be performed once any coagulopathy has been corrected and following platelet transfusion if necessary. The threshold for platelet transfusion is not clear and it depends on the presenece of other risk factors such coagulopathy.
3.2.2. Appropriate handling of diagnostic specimens
Freshly obtained presentation samples of peripheral blood and marrow are suitable for MGG staining and cytochemical tests69. Slides for MPO staining will last for four weeks if kept in the dark at 4ºC. Sudan Black staining is not light sensitive and will not fade over time. Heparinised samples for immunophenotyping, cytogenetics and molecular studies should be kept at room temperature and processed within 24 hours. These specialised tests take time for completion, hence the initial diagnosis and treatment plan will be made on morphology and cytochemistry supplemented by immunological studies.
4.1. Staging procedure
Table 4. Standard practice
Other medical conditions – past and current
Pre-existing MDS or other marrow disease
Occupational risk factors
Drug history (including allergy)
Family history, including siblings
Abdomen, hepato-splenomegaly, teste s
Ophthalmical & neurological examination
|Laboratory||FBC + differential, Blood group
Cytochemistry of PB and/or BM blasts (MPO or SBB, ANAE)
Immunophenotyping to confirm myeloid origin Cytogenetic studies of BM /or PB blasts
Liver and kidney function, albumin, LDH
Glucose, uric acid, calcium and phosphate
Coagulation screen, immunoglobulins
Class I and II HLA typing of patient and siblings
Baseline virology [HBsAg, CMV IgG, HCV IgG, VZV IgG]
|Other tests||ECG & chest X-ray|
|Invasive procedures||Bone marrow aspirate ± trephine biopsy|
Consider further investigations (e.g. lung function, ECHO, lumbar puncture) depending on individual clinical status and the presence of host or disease related complications.
4.2. Staging classification
AML is a disseminated disease at diagnosis hence staging systems similar to those used for solid tumours are unhelpful and have therefore not been proposed. It is recommended that patients be divided on the basis of a variety of clinical and non-clinical factors (in particular the diagnostic karyotype) into 3 risk groups – ‘good’, ‘standard’ and ‘poor’. This should then be the basis for discussions regarding prognosis and treatment.
5.1. Natural history
Untreated AML is typically fatal over a period of days to weeks depending largely on the level of the blast count in the peripheral blood and on the presence of complications of marrow failure, tissue infiltration or hyperuricaemia. Most patients will die from overwhelming sepsis, significant haemorrhage or as a result of pulmonary or cerebral leucostasis.
The likelihood of achieving a complete remission (CR; for definition see section 9) will depend on many factors and as a result of this heterogeneity CR rates can vary from between 40% to 80%, depending on the particular patient population being studied. Approximately 10 – 20% of those treated will die during induction therapy before remission status is evaluable. This proportion of ‘induction deaths’ rises with increasing age. A further 10 – 20 % of patients will have refractory disease and first line therapies will fail to bring about CR. A further significant proportion will relapse in the first 1 – 2 years following therapy. Of those with refractory and relapsed disease, few will achieve remission and their overall survival is less than 10% with current salvage therapies.
5.2. Prognostic factors
5.2.1. Secondary AML
AML arising on a background of prior myelodysplasia or following chemotherapy is associated with reduced CR and overall survival rates.
Biological age is a highly significant prognostic variable adversely affecting both attainment of remission and relapse risk. It has been repeatedly demonstrated in many studies that prognosis worsens with increasing age, both in terms of response and overall survival. For those patients less than 60 years, CR rates of 75% and 5-year survival rates of 35 – 40% can be expected. Once the patient age exceeds 60 years, CR rates fall to 45 – 55% and 5-year survival rates fall to less than 10%. The reasons for this include a reduction in the capacity of the patient to tolerate intensive therapy as well as a change in the nature of the disease to one characterised by a higher frequency of adverse cytogenetics, CD34 positivity and MDR-1 expression.
5.2.3. Leukocyte counts
Higher WBC counts are associated to increased induction deaths and more frequent relapses after CR achievement70,71. High WBC counts also associate to other adverse features such as CNS involvement and FLT3/ITD. There is not an established value of WBC above of which the prognosis is considered adverse, although 50×109/l is a frequenly used cutt-off.
5.2.4. Response to therapy
The time taken to clear leukemic blasts from the peripheral blood or the marrow after 1 – 2 courses of induction chemotherapy is an important guide to outcome. The UK MRC consider a blast count of greater than 15% after course 1, or greater than 5% after course 2, as indicative of poor prognosis. The German AMLCG group reported that failure to achieve blast clearance by day 16 is a poor prognostic marker72. This concept is likely to be developed in investigational studies looking at the significance of minimal residual disease (MRD). Persistent MRD-positivity by immunophenotyping, FISH or molecular analysis is recognized as an indicator of increased relapse risk23,24.
An abnormal karyotype is observed in approximately 60% of patients and is highly predictive of response. This has been confirmed in several studies both in younger and older patients73,74. It is now recommended on a type C basis to identify risk subsets based on diagnostic cytogenetics.
Roughly 25% of patients will have ‘favourable’ cytogenetics which include t(15;17), inv 16, t(16;16) and t(8;21). This is irrespective of whether they are detected by G-banding, FISH or molecular methods. These translocations are more common in younger patients and in de novo AML and are associated with CR rates of over 90% and a 5-year survival of around 65%. Often there are additional cytogenetic abnormalities such as -X, -Y and +8 in association with the ‘favourable’ abnormality. However, these additional cytogenetic changes (even if adverse) appear to be of little importance if they are in association with good risk translocations73. Several adverse prognostic factors exist for t(8;21) AML including CD56+ positivity75, the presence of extramedullary disease76, elevated white cell count77 and possibly associated del(9)q78.
10% of patients will have ‘adverse’ cytogenetics, which include -7, -5 del (5) q, abnormalities of 3q21q26 or a complex karyotype73,74. These patients tend to be older, often with prior history of myelodysplasia or exposure to chemotherapy and can expect CR rates of around 60% and a 5-year survival of 10%.
The remaining 45 – 60% of patients will have ‘intermediate’ cytogenetics. The majority of these will have a normal karyotype with no identifiable genetic abnormality on G-banding. The CR rates for this group are about 80% with 5-year survival of 30 – 40%.
There are differences in definition of cytogenetic risk groups between research groups. A ‘complex karyotype’ is defined by the MRC as ≥ 5 unrelated karyotypic abnormalities73 and by the SWOG as ≥ 379. The SWOG also include t(6;9), and t(9;22) as poor risk cytogenetic abnormalities. This has not been replicated by the MRC. Debate continues over the significance of translocations involving 11q23, which are defined as ‘poor risk’ by several groups, particularly in the setting of pediatric AML. This has not been confirmed by the MRC in the UK for adults and is likely to reflect the heterogeneity of MLL gene fusion partners. As a result of these varied definitions, patient distribution among the 3 risk groups may be different between study centers and should be considered when comparing the results of treatment.
Fms-like tyrosine kinase 3 (flt-3) is the receptor for flt-ligand, belonging to the same family as the KIT and the PDGF receptor34,35. It is involved in normal haemopoiesis and is expressed by AML blasts in a significant proportion of cases. In-frame internal tandem duplication [ITD] mutations of exons 14-15 have been noted in 15-30% of cases of AML. This elongates the juxtamembrane segment of flt-3 resulting in its dimerization and constitutive activation80. Such ITD mutations occur across FAB types and are particularly frequent in M3. They primarily occur in ‘intermediate risk’ patients and are more frequent in adults than in children81. ITD mutations of FLT3 have been shown to be an independent poor prognostic factor in several studies47-49,82 and mutation status can delineate a ‘poor risk’ group from a previously homogeneous ‘intermediate risk’ group. Biallelic mutations are noted in approximately 10% and are associated with an even poorer outcome.
Additionally, point mutation of codon 835 of FLT3 has been reported in 7 – 8% of cases of de novo AML83. This mutation results in up-regulation of the function of the kinase domain, the prognostic significance of which is controversial. Such mutations have also been found in ALL associated with cytogenetic hyperdiploidy or abnormalities of MLL84 as well as in myeloid sarcoma85. Increasing numbers of tyrosine kinase domain mutations at other codons are being reported39.
NPM1 is a gene encoding a nucleus-cytoplasm shuttling protein, located at chromosome band 5q35. In normal situation, nucleophosmin is most prominent in the nucleus; in contrast, patients with mutated NPM1 show cytoplasmic expression, which interferes its normal function. Cytoplasmic localisation of nucleophosmin by immunostaining is observed in approximately half of CN-AML patients and associates with good response to induction chemotherapy and long EFS21,86.
About 40% of NPM1 mutated cases have also FLT3-ITD. Of note, NPM1 mutations are a favorable prognostic indicator only in subjects with wild-type FLT3 (ie, NPM1+/FLT3-)87.
EVI1 gene is overexpressed in patients with inv(3), t(3;3), and in minority of AML with a normal karyotype45,88, being associated with a poor prognosis.
Twenty to 30% of patients with AML and favorable cytogenetics such as t(8;21) or inv(16) have KIT gene mutations50,51. These mutations have adverse prognostic impact due to increased relapse risk.
Translocations involving 11q23 and different chromosomal partners might be observed in primary and therapy-related AML. The most frequently identified are t(9;11) (p22;q23), t(11;19)(q23;p13.1) and t(6;11)(q27;q23)33.
In some patients with AML and either trisomy 11 or a normal karyotype, a fusion occurs between one of the exons in its breakpoint cluster region and the 5′ sequences from MLL itself. These partial duplications of MLL in patients with CN-AML associated to short CR duration in most studies89-92 but not in all93.
22.214.171.124. CEBPA (CCAAT enhancer binding protein alpha)
CEBPA gene mutations at both the N – and C- termini are found in approximately 10 % of cases of AML, primarily in M1 and M2 ‘intermediate risk’ cases. These mutations have been associated with a favorable outcome in adults with a normal karyotype53.
The expression of Wilms tumor suppressor gene (WT-1) is increased in blast cells of 75 percent of newly diagnosed AML42. High WT-1 levels have been to associated to adverse outcome in terms of CR achievement and overall survival42.
In adults up to 59 years of age with de novo CN-AML, a high expression of BAALC mRNA in circulating blasts has been associated to adverse clinical outcome in three independent studies43,94-96.
ERG gene located in band 21q22 is a member of the ETS family of genes which are down-stream nuclear targets of signal transduction pathways. These genes regulate and promote cell differentiation, proliferation and tissue invasion97,98. Marcucci et al used real-time RT-PCR to analyse ERG expression in a series of 84 CN-AML patients. Those with ERG overexpression showed high relapse rate and poor survival despite being NPM1+/FLT3-ITD negative99.
5.2.7. Other variables
Patients with extramedullary or CNS disease have a poor outcome. Other clinical markers of a high tumour burden such as hepatosplenomegaly or raised serum LDH are in some studies associated with adverse prognosis. Male sex and poor performance status also are seen to affect prognosis adversely.
Variables associated with an above average outcome:
Presence of Auer rods
The expression of a pan-myeloid phenotype [MPO+, CD13+, CD33+, CDw65+ and CD117+].
Variables associated with a below average outcome:
Tri-lineage dysplasia at diagnosis, although this is now believed not to be an independent factor beyond its role as a marker of poor risk cytogenetics100.
FAB types M0, M6 and M7; M5 controversial101.
CD 34 positivity.
Marrow dysplasia evident at remission
5.2.8 Multi-drug resistance
P-gp is a 170kd drug efflux protein coded for by the multi-drug resistance gene 1 (MDR-1) that is selective for anthracyclines and podophyllotoxins102. High levels of p-gp expression result in low intracellular drug concentrations. This is seen in 40% of cases of AML at diagnosis, and expression increases following exposure to chemotherapy as well as with advancing patient age. The prognostic significance of p-gp expression in AML was previously unclear, reflecting variation in methods of analysis. However, the implementation of consensus recommendations for flow cytometry103,104, functional assays and molecular techniques have led to the conclusion that p-gp expression is a negative prognostic factor105-107. Other drug resistance proteins have been identified including MDR-related protein (MRP)108, lung resistance protein (LRP)109,110 and breast cancer resistance protein (BRCP)111,112 yet their roles and prognostic significance remain unclear. The calcein assay that identifies both MDR and MRP positive cells may become increasingly important113,114.
5.2.9 Gene expression profiling
Unsupervised cluster analysis of gene expression patterns using cDNA arrays has begun to identify new groups within normal karyotype AML such as ‘pure normal cytogenetics’ and ‘translocation like’ AML. These two classes have been shown to have different prognosis115. Other studies have also shown the prognostic impact of different patterns of gene expression profiling58-60.
A variety of markers have been identified in the literature as potential prognostic markers. Their role in current practice remains investigational.
Autonomous proliferation in short-term culture.
Expression of pro and anti-apoptotic proteins such as bcl-2116 and bax117.
In vitro sensitivity to anthracyclines or cytarabine and Ara-CTP incorporation118 and Km of 5’nucleotidase119.
Glutathionine-S-transferase enzyme activity120.
Polymorphisms in drug metabolic pathways (SULT1C2) and DNA-repair (XPA) genes115.
Bone marrow microvessel density127.
5.3. Risk groups
It is now standard practice, on a type C basis, to utilise clinical and laboratory features at diagnosis to categorise patients into 1 of 3 discrete risk groups: ‘good’, ‘standard’ and ‘poor’. Age, karyotype and initial response to induction therapy are the prime prognostic variables. Biological features of AML cells, for example FLT3 and NPM mutation status, play also an important role. All patients, irrespective of their risk group should be considered for entry into clinical studies. It is expected that in time the therapies for the different risk groups will diverge to produce a risk-adapted approach to therapy. This is already happening in terms of avoiding myeloablative therapy for those with ‘good risk’ disease and advocating early allografting for those considered being at high risk of relapse.
6.1. Supportive care
6.1.1 Metabolic complications and venous access
An awareness of the possibility of the metabolic complications of instituting therapy in a patient with AML is vital. Although acute tumor lysis syndrome (ATLS) occurs uncommonly in AML, it should be a concern in treating patients with high presenting counts and bulky extramedullary disease. ATLS is characterised by hyperuricaemia, hyperphosphataemia, hyperkalaemia, hypocalcaemia and oliguria129. Allopurinol should be commenced prior to therapy in addition to ensuring a high urine output with intravenous fluids and diuretics as necessary. Regular monitoring of electrolytes and fluid balance is standard on a type C basis. Alkalinisation of the urine by the administration of intravenous bicarbonate or oral acetazolamide remains controversial as it may exacerbate calcium phosphate deposition in organs including the heart and may reduce tubular solubility of xanthine. Urate oxidase [RasburicaseTM] has been shown to be more effective than allopurinol and can be used as an alternative suitable for individual clinical use on a type C basis 130,131. Hypokalaemia may also be a feature at presentation and during induction therapy, particularly in those patients with monocytic leukemias and resultant high serum lysozyme. This requires vigorous intravenous or oral potassium replacement.
Establishment of secure central venous access through a tunnelled Hickman line or a temporary jugular or subclavian central line is recommended on a type C basis prior to starting therapy. This is to enable safe administration of vesicant drugs, facilitate frequent blood sampling and provide access for intravenous medication and blood products. This practice must however be weighed against the finite risks of catheter associated thrombosis and infection. Patients presenting with a high peripheral white count are at high risk from the pulmonary, cardiac and cerebral complications of leucostasis. Leucapheresis brings about rapid cytoreduction and should be considered as suitable for individual clinical use on a type C basis.
6.1.2. Prevention and treatment of Infection
The risk of infection is related to the degree of neutropenia, which may be either a result of bone marrow infiltration or cytotoxic-induced aplasia. Breaches in the integument, such as from intravenous access devices (IAD) or mucositis increase the likelihood of systemic bacterial translocation and alterations in bacterial flora can occur as a consequence of broad-spectrum antibiotic use, gastric acid suppression and prolonged periods of hospitalisation. Fever is often the cardinal sign of sepsis although may sometimes be masked or absent, for example in elderly patients or with the concurrent administration of antipyretics or corticosteroids. Sepsis should be suspected in the presence of any sudden non-specific deterioration in clinical condition, hypotension or new cellulitic changes around an IAD or the oropharynx or perineum. The febrile patient should have central and peripheral blood cultures taken as well as appropriate microbiological cultures of urine and stool. A chest radiograph should complement careful clinical examination of the chest, perineum, oropharynx and IAD. The past decade has seen a shift away from Gram-negative aerobes such as Klebsiella, Pseudomonas, and E. coli as causative agents of sepsis in neutropenic patients towards Gram-positive organisms, such as Streptococcus viridans and Staphylococcus spp, being more frequently isolated. This reflects the widespread practice of quinolone prophylaxis, more frequent IAD use and the greater mucosal toxicity resultant from increases in the intensity of chemotherapeutic regimens. On a recent Cochrane review, antibiotic prophylaxis significantly decreased the risk for death when compared with placebo or no intervention (RR 0,67 [95% CI, 0,55 to 0,81]) as well as the risk of infection-related death (RR 0,58). The most significant reduction in risk for all cause mortality was observed in trials assessing prophylaxis with quinolones (RR 0,52 [95% CI, 0,35 to 0,77]). Despite the occurrence of adverse effects and development of resistence the benefit of prophylaxis was obvious since all cause mortality was reduced. It is recommended on a type 1 level evidence to give antibiotic prophylaxis with a preference for a quinolone. Fungal prophylaxis with fluconazole has been shown to reduce systemic or invasive fungal infections but with a reduction in mortality only for patients undergoing haemopoietic stem cell transplantation. Fluconazole has little activity against Aspergillus spp. and there is evidence that it selects for resistant strains of Candida, especially C. kruseii and glabrata spp. It is therefore suitable for individual clinical use on a type 2 evidence. Itraconazole has a broader spectrum of activity and has been shown to reduce fungal infections and associated mortality132. However, patient compliance and pharmacokinetic considerations make itraconazole difficult to use effectively in clinical practice. New antifungal agents have been developed, such as lipid formulations of amphotericin, caspofungin, voriconazole and posaconazole, among others. Recently, the guidelines on the relative value of these new agents as prophylaxis or treatment of Aspergillus infections have been updated133. Primary CMV infection can be prevented by the use of blood products from CMV IgG negative donors in CMV seronegative patients or by the use of leucocyte depleted blood products.
Standard empirical therapy for febrile neutropenia based on a type C basis comprises either monotherapy with a third generation cephalosporin or carbapenem or combination therapy given for at least 10 – 14 days. Combination therapy should consist of either a broad-spectrum penicillin or cephalosporin in addition to an aminoglycoside. Local microbiological advice, based on the resistance patterns of the most prevalent bacterial isolates, should guide the exact choice of antibiotic therapy. The addition of vancomycin or teicoplanin as a third drug to broaden Gram-positive cover is recommended on a type R basis if there are concerns over IAD infection or a high local frequency of MRSA infections, however their routine empirical use is not recommended on a type 1 level of evidence. Further modifications to the initial antibiotic regimen should be based on culture results and clinical examination. If the patient remains febrile despite negative culture results, consideration should be given to occult fungal infections, viral infections or non-infectious causes of fever, such as drug reactions. It is standard practice on a type 2 level of evidence to start antifungal agents after 4 – 7 days of pyrexia in patients with severe neutropenia and inconclusive blood culture results. Use of granulocyte transfusions is problematic, complicated by alloimmunisation, febrile reactions, pulmonary infiltrates and primary CMV infection134. Their use should therefore be considered as suitable for individual clinical use on a type 3 level of evidence.
Life-threatening bleeding has been noted to affect 1% of patients at presentation, 5.5% – 7% during induction and 17 – 33% during induction in association with infection135. Such bleeding usually occurs in the context of disseminated intravascular coagulation (DIC) with hypofibrinogenaemia or a platelet count under 20 x 109/l and this risk may be further increased by pulmonary infection or hyperleucocytosis. Death from haemorrhage during consolidation is less common, occurring in approximately 2% of cases, although this rate increases with advancing age. The use of prophylactic transfusions of either single-donor apheresis or multiple-donor pooled platelet concentrates is recommended on a type C basis to reduce the rates of significant bleeding. The threshold for such platelet transfusion remains a subject of debate. It is currently standard to transfuse one adult dose of platelets if the platelet count is below 10 x 109/l and the patient is otherwise well and not bleeding, 20 x 109/l if the patient is septic, is on antibiotics or has abnormalities of haemostasis and 50 x 109/l if the patient is actively bleeding136,137. Patients who achieve poor 24-hour increments to fresh ABO-compatible single donor platelets should be screened for the presence of anti-HLA alloantibodies and the need for HLA-matched platelets discussed with the regional transfusion centre. APL, particularly the microgranular variant (M3v), is associated with a 10% incidence of significant haemorrhage, although this has fallen with the introduction of ATRA into remission induction therapy. Transfusion of platelets should be standard during induction with a view to maintaining a platelet count greater than 10-20 x 109/l in the absence of bleeding and greater than 50 x 109/l if there is active bleeding. Human fibrinogen should be infused to maintain the fibrinogen above 1g/l with the addition of fresh frozen plasma if either the prothrombin time or the activated partial thromboplastin time is prolonged in association with active bleeding. Heparin has not been shown to be of any significant benefit in APL in either reducing early deaths due to bleeding or improving remission rates or overall survival138. Its routine use cannot be recommended on a type 1 level of evidence. Fibrinolytic agents, such as tranexamic acid, should also be used as suitable for individual clinical use in cases of incipient life-threatening intracranial haemorrhage based on a type R basis.
6.2. Antileukemic treatment
6.2.1 Remission induction chemotherapy
The aim of induction therapy is to produce maximal tumour destruction in order to restore normal haemopoiesis. For the past three decades this has been achieved with an anthracycline plus cytarabine139. Most of such regimens result in complete remission (CR) rates of 65 – 85% in those under 60 years and this remains the standard of care on a type C basis. There is uncertainty as to the best anthracycline to use. Daunorubicin appears better than doxorubicin with less gut toxicity. The CR rate for daunorubicin is higher at a dose of 45 mg/m2 compared to 30 mg/m2, however there is no survival advantage140. Currently, a commonly used dose of daunorubicin is 60 mg/m2. Several randomised studies have suggested that idarubicin is superior to daunorubicin in dose of 45 mg/m2, in patients under 50 years141. More patients achieve remission after the first course and the duration of this remission is longer142-144. Idarubicin has better CNS penetration, lacks p-gp modulation, has a longer half-life and is metabolised into active compounds. However, it is more myelosuppressive and hepatotoxic and any survival advantage lessens with increasing patient age. Standard therapy on a type C basis consists of either daunorubicin or idarubicin given for three days. Other anthracyclines such as mitoxantrone can be considered as suitable for individual clinical use on a type 3 level of evidence.
Cytarabine is traditionally given 100 – 200 mg/m2/day as either a continuous infusion or intermittent iv injections. The same results are achieved for 100 and 200 mg/m2/day as a continuous infusion given for 7 days or intermittent injections given for 10 days145,146. Gastro-intestinal toxicity is higher if the cytarabine is given as an infusion. High-dose cytarabine has been used for induction at doses of 1 – 3 g/m2 bd for 4 – 6 days and high CR rates have been observed in uncontrolled trials147. In randomised studies there was no significant improvement in CR rate but there was a beneficial effect on disease free survival148-151. This remains a subject of debate. It is clearly advantageous to receive one or more course of cytarabine at gram/m2 doses, however there are many who would prefer to give such blocks of treatment as consolidation once remission has been achieved. Standard therapy on a type 1 level of evidence is 100 – 200 mg/m2/day for 7 days as a continuous infusion or 100mg/m2 bd for 7 – 10 days as bolus injections. Intermediate and high doses of cytarabine may be considered as suitable for individual clinical use or as part of a clinical trial based on a type 2 level of evidence.
There has been interest in adding a third drug to an anthracycline and cytarabine combination. 6-thioguanine (6TG) was initially used but has not been shown to offer any benefit in terms of remission induction, remission duration or overall survival. The addition of etoposide improves remission duration but not CR rates or overall survival and any benefits noted were only seen in those under 55 years152. Studies comparing a thioguanine-containing regimen (DAT) to an identical one containing etoposide (ADE) found no significant difference between the two153,154. The addition of a third drug is therefore optional and should only be considered suitable for individual clinical use, on a type 1 level of evidence. Fludarabine given prior to cytarabine blocks its metabolism and hence increases ara-CTP levels155. Regimens utilising this approach may be suitable for individual clinical use on a type 3 level of evidence.
Recently, the MRC group has shown that the addition of gemtuzumab ozogamycin to the induction chemotherapy with ADE or FLAG-ida decreased relapse rate from 52% to 37% at 3 years and improved DFS from 40% to 51% in patients with AML, particularly in the favourable and standard risk groups156.
Different cooperative groups in Europe and the US are currently investigating to associate new agents such as zosuquidar, a potent PgP modulator, FLT3 inhibitors, or farnesyltransferase inhibitors, among others157.
Table 5. Examples of Induction Regimens
|Regimen||Drugs and schedule|
|3 + 7||Daunorubicin 50 mg/m2 iv per day, 3 days
Cytarabine 100 – 200 mg/m2 per day, 7 days
|DAT||Daunorubicin 45 or 60 mg/m2 iv per day, 3 days
Cytarabine 100 – 200 mg/m2 iv per day, 7 or 10 days
6-thioguanine 100 mg/m2 po per day, 7 or 10 days
|ADE||Daunorubicin 50 or 60 mg/m2 iv per day, 3 days
Cytarabine 100 mg/m2 iv per day or bd, 7 or 10 days
Etoposide 100 mg/m2 iv per day, 3 or 5 days
|MAE||Mitoxantrone 12 mg/m2 iv per day, 3 days
Cytarabine 100 mg/m2 iv bd, 10 days
Etoposide 100 mg/m2 iv per day, 5 days
|ICE||Idarubicin 10 or 12 mg/m2 iv per day, 3 days
Cytarabine 100 mg/m2 iv per day or bd, 7 or 10 days
Etoposide 100 mg/m2 iv per day, 3 or 5 days
|FLAG Ida||Fludarabine 30 mg/m2 iv per day, 5 days
Cytarabine 2 g/m2 iv bd per day, 5 days
Idarubicin 10 mg/m2 iv per day, 3 days
G-CSF 5 mcg/kg/day s/c from day 1
|HIDAC-3-7||Daunorubicin 50 mg/m2 iv per day, 3 days
Etoposide 75 mg/m2 iv per day, 7 days
Cytarabine 3 g/m2 iv in 3 h / 12 h days 1,3,5,7
6.2.2. Side effects and complications of remission induction chemotherapy
The common side effects of cytotoxic chemotherapy include marrow suppression with requirement for red cell and platelet support and risks of neutropenic sepsis. This is more significant with the use of idarubicin or the addition of a third drug. Ten percent of patients up to 65 years of age will die during induction therapy, typically as a result of sepsis or bleeding consequent on bone marrow suppression. The proportion is higher in elderly patients. Gastrointestinal toxicity with consequent mucositis, nausea, vomiting and diarrhoea is also common. This is more pronounced with doxorubicin as compared to daunorubicin and is more likely with infusional rather than bolus cytarabine administration. Alopoecia and fatigue occur frequently. Fertility may be lost as a result of AML therapy, therefore it is recommended on a type C basis that all males be offered the opportunity for semen cryopreservation prior to starting therapy, provided that treatment is not delayed or compromised. High doses of cytarabine (1g/m2 and above) are associated with colitis, cerebellar toxicity, conjunctivitis and a blistering erythematous rash particularly affecting the hands and feet. Daily examination for cerebellar signs and prophylactic steroid eye drops are therefore recommended on a type C basis in this group of patients. Cerebellar toxicity is primarily seen in the elderly and those with renal impairment. In case of neurological complications cytarabine should be stpped immediately.
6.2.3. Growth factors during remission induction
Granulocyte colony stimulating factor (G-CSF), granulocyte/macrophage colony stimulating factor (GM-CSF) and more recently pegfilgrastim, the pegylated long half-life modification of G-CSF158, have been used in association with induction chemotherapy. These agents shorten the duration of severe neutropenia (< 0.5 x 109/l) by between 2 – 6 days; however, the majority of studies show no beneficial effect on either CR rate or survival. The use of growth factors entails additional costs and they have side effects, such as fever, that may cause diagnostic confusion. In one study, the use of G-CSF prior to and during chemotherapy as cell-cycle primer was shown to be of benefit for patients with intermediate-risk AML, in terms of remission duration and overall survival159. This finding has to be confirmed in further studies before a recommendation on this indication can be made. Concern over potential stimulation of myeloid blasts by growth factors has not been justified. Current recommendations for the use of CSF’s advise weighing their potential benefits against their cost. Their routine use cannot be advocated on a type 1 level of evidence however they may be suitable for individual clinical use, especially in older patients160,161.
6.3. Principles of continuation (post-remission) therapy
6.3.1 Consolidation therapy
Without post-remission consolidation therapy, the median remission duration is 4 months. It is therefore standard practice on a type C basis to give consolidation chemotherapy. This typically tends to be 1 course of therapy similar to that used for induction, followed by 2 to 4 coures including intermediate or high-dose ara-C, together with amsacrine and/or mitoxantrone or etoposide.
Table 6. Examples of Consolidation Regimens
|Regimen||Drugs and schedule|
|MACE||Amsacrine 100 mg/m2 iv D 1 – 5
Cytarabine 200 mg/m2 continuous infusion D 1–5 [5 doses]
Etoposide 100 mg/m2 iv D 1 – 5
|HAM||HAM Cytarabine 3 g/m2 3 hr infusion bd D 1 –3 [6 doses]
Mitoxantrone 10 mg/m2 iv D 3 – 5
|Intermediate / High dose ARA C||Cytarabine 1 – 3g /m2 bd D 1 – 4 to 6 [8 -12 doses]|
continuous infusion D1 – 2 [2 doses]
bolus bd D 3 – 8 [12 doses]
Daunorubicin 60 mg/m2 iv D 3 – 5
|ICE||Idarubicin 10 mg/m2 iv D 1 – 5
Cytarabine 100 mg/m2 bd iv D 1 – 5 [10 doses]
Etoposide 100 mg/m2 iv D 1 – 5
|MiDAC||Mitoxantrone 10mg/m2 D 1 – 5
Cytarabine 1g/m2 iv bd D 1 – 3 [6 doses]
|AMSA/ARA-C (HOVON)||AMSA 120 mg/m2 iv D 3, 5, 7
Cytarabine 1 g/m2 3 hr infusion q 12 hrs D 1–6 [12 doses]
It is important to balance the benefits of further therapy against the potential risks of toxicity. For example, there is a type 1 level of evidence that 4 courses in total may be as effective as 5162. However, even despite consolidation therapy many patients will relapse. A CALGB study suggests that increasing the dose intensity does appear to be of benefit in terms of remission duration and survival for those who received intensive cytarabine at a dose of 3 g/m2 compared to 400 mg/m2 or 100 mg/m2 doses163. Subgroup analysis suggested that patients with CBF leukemias appeared to benefit the most164, although this approach was limited by the toxicity of high-dose cytarabine in older patients164,165.
6.3.2. Central Nervous System (CNS) prophylaxis
CNS disease in AML is uncommon at presentation, therefore a diagnostic lumbar puncture is not standard in the absence of symptoms or signs to suggest CNS involvement. It is recommended on a type R basis that patients with FAB types M4 or M5 or high WBC counts at diagnosis, or with leukemia cutis who are at increased risk of CNS disease, have a single CSF examination to exclude occult disease. This should ideally be once the blasts have cleared from the peripheral blood and involve the intrathecal instillation of methotrexate or cytarabine. The impact of treatment regimens containing high-dose cytarabine, which penetrates the blood-brain barrier well, may make this intervention less important. CNS relapse is rare in adult AML therefore routine prophylaxis is not recommended, however clinicians may wish to consider this approach as suitable for individual clinical use, particular in case of leukemia cutis.
Maintenance chemotherapy in AML is typically less intensive and myelosuppressive than standard consolidation cycles, usually involving short courses of subcutaneous cytarabine combined with oral agents such as a thiopurine or etoposide given for 2 –3 years. Maintenance may prolong initial remissions but is of no benefit in improving overall survival rates166 and is not recommended on a type 2 evidence if post-remission therapy is of adequate intensity.
6.4. AML in pregnancy
Though with a similar prognosis than that observed in non-pregnant, AML during pregnancy represents a challenging situation. Management should involve both hematologists and obstetricians. Administration of chemotherapy during the first trimester is associated with a high risk of fetal malformations and abortion167,168 and, if possible, it is not recommended on a type C basis. In this situation, mother should be correctly informed and termination of pregnancy is recommended on a type C basis. If termination of pregnancy is unacceptable then chemotherapy can be offered under the risks previously described because delay in AML treatment is associated with an adverse prognosis.
At the second and third trimester, the risk of malformations decreases and treatment with chemotherapy is recommended on a type C basis. However, an increased risk of abortion, premature delivery and low birth weight has been observed169.
6.5. Hematopoietic transplantation
6.5.1. Autologous stem cell transplantation
Autologous stem cell rescue using bone marrow or peripheral blood taken in remission, allows the administration of myeloablative doses of chemotherapy or chemoradiotherapy170,171. This approach has been shown in non-randomised studies to produce a 45-55% disease free survival. Autografting has been evaluated in multiple studies as consolidation therapy, both instead of and in addition to chemotherapy172-175. It has been demonstrated to reduce the risk of relapse, although this positive effect is counterbalanced by a 5-15% procedure-related mortality. Also of note, many patients who were randomised to receive an autograft in fact did not proceed to transplantation and this low penetrance may in fact underestimate the anti-leukaemic efficacy of autografting. In practically all studies, overall survival was the same in patients in first CR treated with chemotherapy and those who were autografted. This is especially true for those patients who received high-dose cytarabine as consolidation.
Given these results and the long-term effects on fertility, sexual health, quality of life and second malignancy, autografting is not standard therapy for first CR on a type 1 level of evidence and type 2 confirmatory trials would be desirable. It may be suitable for individual clinical use in first or second CR on a type 3 level of evidence. This includes patients with poor-risk AML in first remission without an allogeneic donor, those in second remission with a long first CR or those with favourable cytogenetics. The use of blood rather than marrow-derived stem cells has led to faster haematologic recovery and mortality rates around 5%176. Purging with positive selection for CD34+ cells or negative selection using chemotherapy or monoclonal antibodies to reduce tumour contamination of the autograft has not been shown to improve the results and these approaches remain investigational on a type 3 level of evidence.
6.5.2. Allogeneic stem cell transplantation
Conventional allografting allows intensification of therapy in addition to harnessing a ‘graft-versus-leukemia’ effect in order to reduce relapse risk. Unfortunately problems regarding conditioning regimen related toxicity, graft-versus-host disease (GVHD) and infection result in a 20 – 25% transplant-related mortality and generally limit the procedure to those under 50 years old. Despite this, allografting remains the most effective anti-leukaemic treatment with a relapse risk of 20 – 25%. Unfortunately excess toxicity results in a 5-year survival of 50-55% for allografts performed in first CR. Outcome is related to patient age with more than 60% 5-year survival for patients under 20 years and 40-50% for those over 20 years. Outcome is also related to transplant timing whereby those transplanted in first relapse or second CR have a 20 – 30% 5 year survival and those transplanted with advanced disease have a 10-15% 5 year survival. The disadvantage of allografting in first CR is that it exposes patients who are potentially cured with chemotherapy alone to the 1 in 4 risk of death from a transplant procedure and the long-term morbidity of chronic GVHD. For this reason, some authors argued that it is better to allograft in early relapse or in second CR, if that can be achieved.
There have been no direct randomised comparisons of chemotherapy and allografting although some studies using so-called biological randomisation between donor/no donor have shown a benefit for allografting in first CR in certain subgroups79,177-181. In controlled trials, HLA-identical sibling transplantation improved the outcome of patients with high-risk cytogenetics in the US intergroup and EORTC-GIMEMA studies79,178. In the first of these two experiences, transplantation also offered better results than intensification chemotherapy in patients with a favorable karyotype79. In contrast, in the large Medical Recearch Council (MRC) series, HLA-identical sibling transplantation was the best option for patients with intermediate-risk features177. These studies are summarized in recent meta-analyses and evidence-based reviews showing that allogeneic transplantation is of benefit in the high-risk cytogenetics group179-181. Also, there is considerable international variation in attitude towards the role of hematopoietic transplantation in first CR. An interesting series of published reviews and meta-analyses outlined the differences in approach to this situation182-185. Whilst there is a clear reduction in relapse risk associated with stem cell transplantation, this is offset by the significant transplant-related mortality and increased long-term morbidity resulting in no clear survival advantage186. Quality of life after treatment has also to be considered. In this regard, an analysis of patients allografted in the UK AML 10 study showed an adverse impact of this procedure on mouth dryness, sexual and social relationships and professional and leisure activities compared to autografting187.
Good risk patients have a significant chance of cure with standard chemotherapy and salvage rates are high at recurrence188. It is appropriate that allografting should therefore be delayed until disease recurrence. For poor risk patients, allografting may or may not be of benefit, although realistically there is little to offer this group except an allograft in first CR189. Standard risk patients may also be a group to gain benefit from transplantation in terms of overall survival185. However, this could not be the case in adults over 35 years.
The exact role of transplantation in first CR must still therefore remain the subject of clinical trial. It may be possible to identify new prognostic factors, such as FLT3 or CEBPA that yield important information on relapse risk, or the chances of achieving a second CR. Such information will aid in selecting those patients to undergo allografting in first CR.
Unrelated and mismatched related donor transplants are associated with a higher risk of transplant-related mortality and should therefore be reserved for individual patients at relapse or those in first CR at high risk of relapse190,191. A recent report shows that long-term leukemia-free survival may be achieved in a substantial proportion of patients with poor-risk cytogenetics AML who receive an unrelated donor graft192. These results seem better than those obtained with chemotherapy only. Non-myeloablative allografts using varying reduced intensity conditioning regimens are less hazardous and allow the procedure to be carried out in patients over 50 years or in those with significant comorbidity193-197. The risks of GVHD and immunosuppression remain, however, and therefore these approaches despite encouraging should be considered investigational.
6.6. Summary of treatment strategy
6.6.1. Front-line treatment
Optimal supportive care and remission induction chemotherapy is standard on type C basis. There remains uncertainty over the anthracycline, however either 45 or 60 mg/m2 daunorubicin or 10 – 12 mg/m2 idarubicin for 3 days as intravenous bolus injections are standard. This should be combined with cytarabine given as either 100 – 200 mg/m2/day for 7 days as a continuous infusion or 100 mg/m2 bd for 7 – 10 days as intermittent injections. A third drug, such as etoposide or 6-thioguanine, can be considered as suitable for individual clinical use on a type 3 level of evidence. The addition of other agents remains investigational. In elderly patients with unfavourable cytogenetics and without an option for allogeneic stem cell transplantation, and those unfit for intensive chemotherapy, therapy may be limited to supportive care or low-dose cytarabine.
6.6.2. Post-remission strategy in ‘good risk’
Between 2 – 4 cycles of post-remission consolidation therapy should be given as standard on a type C basis. Intermediate/high doses of cytarabine should be included in at least one of these cycles as standard on a type 2 level of evidence. The optimal cytarabine dose level remains to be elucidated. There is no role for allografting or autografting in CR1 in this group of patients, with such treatment remaining investigational, although adverse associated features as WBC counts and/or C-KIT mutations justify to explore this approach.
6.6.3. Post-remission strategy in ‘intermediate risk’
This group forms the majority of AML patients and is biologically heterogeneous. For this reason, any effort should be done for further subdividing this large and basically undetermined group of patients into more refined prognostic subgroups. This may be achieved by considering collateral clinical risk features and especially by investigating additional genetic lesions and MRD status, eventually leading to an improved risk-oriented therapy. In this sense, it is now accepted that patients with FLT3-ITD have a poor prognosis; in contrast, those without this molecular abnormality carrying NPM1 mutations have a favourable outcome and transplantation in this group could not be justified in CR1, the same accounts for CEBPA mutations. Anyhow, between 2 – 4 cycles of post-remission consolidation therapy should be given to all patients as standard based on type C basis. Intermediate/high doses of cytarabine should be included in at least one of these cycles as standard on a type 2 level of evidence. High dose therapy may be suitable for individual clinical use on a type 3 level of evidence. Routine HLA-matched related donor allografting using myeloablative conditioning in those under 40 – 50 years and non-myeloablative conditioning in older patients remains a subject of considerable debate across the speciality and is therefore an approach to be evaluated in the context of clinical trials.
6.6.4. Post-remission strategy in ‘poor risk’
Post-remission consolidation therapy should be given as standard based on type C basis although the relapse rate is disappointingly high and the benefits of intermediate/high doses of cytarabine are less clear198. Whether high-dose therapy, including allogeneic transplantation, significantly improves or not the overall survival of this group is controversial79,177-181. The reality is that there is little else to offer these patients to prevent relapse and, for selected patients with high risk disease in CR1, allografting is probably the best treatment available. Therefore transplantation is considered as standard therapy on a type R basis. HLA-matched related donor allografts should be considered as suitable for individual clinical use on a type 2 level of evidence. Unrelated or mismatched adult related donor and umbilical cord blood transplants remain investigational199-202. This group should also be considered suitable for individual clinical use for experimental therapies on a type C basis.
6.7 Salvage therapy for relapsed-refractory AML
Both, relapse or refractoriness, are clearly bad prognostic indicators for the outcome of AML patients. Relapse is expected to occur in about 35% to 76% of the patients achieving CR after frontline therapy according to the three major cytogenetic categories, and it represents the commonest cause of treatment failure73,203. The treatment of these patients is strongly influenced by the limitation of available effective drugs, since the agents with the highest antileukemic activity have been usually used as a first line therapy. The probability to achieve a second CR is highly variable according to different prognostic factors as explained below. If this second response occurs, its duration is usually shorter than the first CR. Generally, there is a trend to indicate allogeneic hematopoietic stem cell transplantation (HSCT) if possible, but performing transplantation is conditioned to the response of a second induction course for relapsed patients or to the number of previous chemotherapy courses for the refractory patients204,205.
6.7.1. Prognostic factors for remission and survival in relapsed AML patients
Several prognostic factors have been identified in patients with relapsed AML. Two of them, duration of first CR and cytogenetics at diagnosis, are the most important of these variables, both for the rate of second CR and for the probability of survival206-212. It is recommended on a type R basis to take into account these two variables to design the treatment strategy in relapsed patients.
Patients with first remission duration longer than 12-18 months have a second CR probability higher than 50% with chemotherapy regimens based on the use of cytarabine. By contrast, patients with duration of first remission shorter than six months are expected to have low response rates to a second standard chemotherapy. In this case, second remission rate could not be higher than 10%209.
Karyotype at diagnosis has also a straight relation with the response rate in relapsed AML patients. According to the MRC classification, a second CR after chemotherapy treatment is achieved in 88% of patients in the favorable group, 64% in the intermediate group and 36% in the adverse group210. The probability of survival at three years is 43%, 18% and 0%, respectively210.
Other factors such older age and previous stem cell transplantation reduce the response rates and the probability of survival206,213.
Based on these considerations, several recommendations could be made at the time to plan a second induction in a relapsed AML patient younger than 60-65 years who is consider fit to receive intensive chemotherapy:
a. Patients with a first CR longer than 6 months or with favorable risk karyotype are candidates to second induction intensive chemotherapy on a type R basis.
b. Patients with a first CR less than 6 months or adverse risk karyotype could be considered for investigational therapies to try to reach second response on a type R basis.
The patients aged more than 60-65 years or those considered unfit to receive intensive chemotherapy could be considered for investigational therapies or palliative treatment on a type R basis.
6.7.2. Induction regimen for relapsed AML patients
There is no consensus about the standard regimen for remission induction in a relapsed AML patient candidate to intensive chemotherapy. However, if conventional chemotherapy is used it seems reasonable to recommend on a type C basis that the schedule would be based on the use of cytarabine, alone or in combination with other drugs. In this sense, one of the most important questions to answer is the optimal dosage of Ara-C. Ara-C has been used at standard, intermediate or high doses, but there is no clear proof of advantage of any of these schedules. In a prospective randomized study, no significant differences were observed in the CR rates for patients with relapsed or refractory AML with the use of high or intermediate doses of citarabine214. Taking into account only the refractory patients there was a trend to a significant better response rate (46% vs. 26%).
A couple of conventional chemotherapy treatment protocols have been used in relapsed or refractory AML. However, information arising from randomized studies is scarce. Some of these schedules as well as results of randomized trials are summarized in Table 7 and Table 8 respectively.
Table 7. Summary of conventional induction chemotherapy schedules for relapsed or refractory AML
|HIDAC||63% of not resistant to conventional dose Ara-C
20% of resistant to conventional dose Ara-C
|HIDAC + MTZ||65% not resistant to conventional dose Ara-C
56% resistant to conventional dose Ara-C
|High dose VP-16 and CY||42%|
|MTZ + VP-16||43%
32% of refractory to two induction cycles
|Ara-C at ID + MTZ||62%|
|FLAG||81% of late relapse
30% of refractory or early relapse
|TAD||51% of first relapse
28% of second relapse
76% of late first relapse
44% of refractory
HiDAC: high dose Ara-C; MTZ: mitoxantrone; CY: cyclophosphamide; Ara-C at ID: intermediate dose of citarabine; FLAG: fludarabine, citarabine and G-CSF; TAD: thioguanine, citarabine and daunorrubicin; EMA: sequential time etoposide, mitoxantrone and citarabine.
Data from literature do not allow to make solid recommendations about the best induction regimen, rather than the general consensus to use cytarabine. The use of high dose Ara-C alone is effective to reach complete responses in about 63% of patients not clinically resistant to conventional dose cytarabine215. For patients clinically resistant to conventional dose cytarabine the response rate falls up to 20% but it can be improved with the addition of anthracyclines, reaching 56% of remissions without a significant increase in toxicity215.
Table 8. Summary of randomized studies of conventional induction chemotherapy schedules for relapsed or refractory AML
|Flu + HDAC
|No effect of G-CSF or ATRA|
HDAC + VP-16
|No differences in overall survival|
HDAC + MTZ
Ara-C at ID + MTZ
|46% vs. 26% in refractory patients|
Flu: fludarabine; ADE: citarabine, daunorrubicine and etoposide; HDAC: high dose Ara-C; MTZ: mitoxantrone; Ara-C at ID: citarabine at intermediate dose
Data from a randomized study suggest that the combination of fludarabine and high dose Ara-C did not result in a higher complete remission rate and its use not recommended on a type 2 evidence223. Similarly, the addition of VP-16 to high dose Ara-C or the dose of Ara-C (high or intermediate) used in combination with mitoxantrone did not improve response to induction214,224. For the latter, only refractory patients showed a benefit of the use of high dose citarabine214.
Hematopoietic growth factors have been used in randomized trials to increase the response rate in relapsed or refractory AML patients. No significant differences have been observed in the CR rate with the use of G-CSF or GM-CSF225,226. Use of priming with hematopoietic growth factors at the induction course in relapsed or refractory AML patients is not recommended on a type 2 evidence and its use remains investigational.
6.8 Allogeneic stem cell transplantation
Allogeneic HSCT is the most important curative option for the vast majority of patients with relapsed AML. This could not be true for patients with good risk cytogenetics and late relapse, because sustained remissions with chemotherapy have been reported227. Long term disease free survival is achieved for a significant proportion of relapsed or refractory AML patients undergoing allo-SCT, both from related or unrelated donors228,229. However, the outcome of allo-SCT is strongly influenced by the disease status at the time of transplant and disease progression is the most common cause of death204. For patients not achieving a second CR after first relapse the probability of survival after allogeneic HSCT is really low204. Taking into account these data the following recommendations could be made:
a. Allogeneic HSCT is recommended on a type C basis evidence for patients in second CR who are fit for this procedure, using myeloablative or reduced intensity conditioning according to the patient characteristics on an individual basis.
b. For patients with good cytogenetics and late relapse the above recommendation is not applicable. These patients can be considered for chemotherapy or autograft on an individual basis.
c. Allogeneic HSCT is not generally recommended on a type R basis for patients not achieving second CR. These patients are candidates to investigational therapies and allogeneic HSCT should be performed on an individual basis.
In the last decades, continuous improvements in many areas of allogeneic HSCT have dramatically extended its indications to encompass a broad variety of malignant and non-malignant diseases, allowing patients with many different clinical conditions to benefit from this procedure. However, the ideal HLA-identical sibling donor is only available for around 30% of patients, making necessary the use of alternative donors if this treatment is to be offered to the highest number of candidates. Unfortunately, the search for an unrelated bone-marrow donor (VUD), results in a success rate not higher than 50–70%. Much research in the field of stem cell transplantation has been focused on the use of alternative sources of cells, including umbilical cord blood (UCB)230,231. Different studies have shown that similar results can be reached with the use of UCB as compared with bone marrow, at least for those VUD mismatched transplants200,201,201. The use of UCB for those patients lacking a suitable VUD can be recommended on a type C basis, mainly in the context of investigational protocols.
Allogeneic HSCT has been usually precluded for patients older than 55 years or those with significant comorbidity because the chemotherapy conditioning regimen related toxicity. However, the efficacy of allografting also depends on the immune graft-versus-leukemia effect (GVL)197. To overcome this difficulty and to offer this procedure to the highest number of candidates, efforts have been focused on reduce the intensity of the conditioning regimen232. The use of reduced intensity conditioning regimens allows extending the indication of allogeneic HSCT up to patients aged around 65 years193,205,233-241. Reduce intensity conditioning HSCT can be recommended on a type C basis for those patients who are unfit to receive myelloablative schedules, preferably in the context of investigational protocols.
Transplant from haploidentical donors remains investigational.
6.9 New therapies
See the specific paragraph below.
6.10. AML in the elderly
The first challenge for the management of AML elderly patients is to define the subset of “older patients”. It is generally recommended on a type C basis to consider patients aged more than 60-65 years as older patients. This age is lower than the median age for AML. It is clear and generally accepted that elderly patients have a poorer outcome as compared with younger patients, with CR rates usually lower than 60% and a short survival time242-253,253-255. However, for many patients this bad outcome relies on the leukemia cell characteristics, mainly cytogenetics and molecular alterations, rather than age.
6.10.1 Specific characteristics of AML in the elderly
Significant differences on the incidence of specific cytogenetics alterations have been reported between young and old patients, as shown in Table 9. Older patients have a higher incidence of bad prognosis cytogenetics and decrease on the number of good prognosis alterations74. The same effect of the three major cytogenetics categories on the rate of CR and survival described in young patients are observed in the elderly, but treatment results are worse for all three categories74,105,198,256-259. For patients with complex karyotype overall survival is about 2%74,259. However, the use of cytogenetics to decide standard induction therapy or investigational therapy is often precluded for the time required to have available information on karyotype. A delay in the induction therapy could result on a worse outcome for older AML patients (reviewed by Estey)242,251. It is recommended on a type C basis evidence to use cytogenetics results for designing post-remission therapy in AML older patients. The same recommendation can not be made at the time of deciding induction therapy.
Table 9. Differences on cytogenetics according to age
|Younger than 55 years (%)||Older than 55 years (%)|
Other prognostic factors
Together with cytogenetics, other variables have an important role on prognosis, both for CR rate and survival. Antecedent hematologic disease, such as myelodysplastic or myeloproliferative syndrome, are present in up to 40% of AML cases in the elderly and they are related to a low CR rate and a low survival probability105,256,260.
AML in the elderly is also characterized for a higher incidence in the expression of the multidrug resistance glycoprotein MDR1 as compared with younger patients105,106,261. This incidence in older patients is up to 71%105. Overexpression of MDR1, encoding for P-glycoprotein, results in active drug extrusion and it confers resistance from AML blast cells to a variety of antineoplastic drugs. The worse prognosis related to overexpression of MDR1 is mainly due to a reduction in the CR rates105,106,261-267.
Older patients are expected to have comorbid conditions, reflected in a worse performance status. Increases in the ECOG functional status of the patient is also a bad prognosis factor and it must be considered for the treatment choice242.
It is remarkably that in addition to these prognosis variables, age remains an important factor in this group of AML older patients.
6.10.2 Choosing treatment for AML older patients
Taking into account that cytogenetics is usually not available at the time of treatment decision, it is recommended on a type R basis that treatment options should be considered taking into account patients’ age, ECOG and the presence of hematological antecedent or secondary leukemia.
Although, there is a trend to generally recommend investigational therapies for AML in the elderly, this point should be detailed242,268. For patients having not bad prognosis factors other than age, standard therapy with an anthracycline and cytarabine could be better242,268. So that, older patients aged less than 80 years with an ECOG 0-1, no previous myelodysplastic or myeloproliferative syndrome, no secondary AML, no infection and a normal renal or hepatic function are recommended for standard treatment on a type C basis if investigational therapy is not expected to result in a clear improvement of the former.
Post-remission therapy should be tailored according to the same prognosis factors including cytogenetics, gene mutations and induction response. Reduced intensity conditioning allo-SCT should be taken into account for these patients considered fit for this procedure (see transplantation).
For patients not candidate for intensive chemotherapy supportive care or investigational approaches are recommended on a type C basis.
6.10.3 Treatment for AML in the elderly
Combination of anthracyclines and conventional dose cytarabine is recommended on a type C basis as the standard induction therapy for older AML patients, with a type 2 level of evidence163,244,251-255. The use of mitoxantrone or idarubicin rather than daunorubicin has not demonstrated clear advantages244,251. Priming with hematopoietic growth factors during induction in AML older patients is not recommended as standard procedure with a type 2 level of evidence251. Similarly, the generalized use of hematopoietic growth factors during induction is not recommended on a type 2 level of evidence because although it can slightly shorten the number of days to neutrophyl recovery, this does not result in less treatment related deaths or an improve of the overall survival254,269-272. Hematopoietic growth factors could play a role in neutropenic fever, although there is no straight evidence to recommend its use.
6.10.4 Postremission therapy
For patients achieving CR it is recommended on a type C basis to administrate consolidation therapy (one or two cycles) using a similar schedule than induction. Some data, suggest than maintenance therapy with low dose citarabine could improve disease free survival having no impact in the overall survival244.
As explained before and taking into account the results of reduced intensity conditioning it could be recommended on a type R basis to consider it for patients fit for this procedure.
6.10.5 Supportive therapy
Elderly AML patients not clinically eligible for intensive chemotherapy induction treatment or specific investigational therapies must receive the best supportive care. This includes blood and platelet transfusion when necessary and the use of antibiotics to treat or prevent infections. Although hydroxyurea can be used for cytoreduction, low dose cytarabine is considered the best palliative treatment273.
6.11 Definition of response and re-staging
First objective in the treatment of AML is to achieve a complete response. It is strongly recommended on a type C basis to perform a carefully evaluation of response. Although usually not enough, the achievement of CR is a necessary event to cure leukemia. At time, CR is the only response resulting in a clear benefit for the patient. Once CR has been achieved, clinically most relevant is the “quality” of the CR. It is recommended on a type C basis to study the minimal residual disease (MRD) through standardized flow cytometry techniques.
6.11.1. Response criteria
According to previous consensus, we can define different response categories as it is pointed below274.
6.11.2 Complete remission
Complete response to induction therapy as morphologic criteria implies a bone marrow aspirate with less than 5% of blast cells without Auer rods and full hematological recovery in peripheral blood (more than 1 x 109/L neutrophils, more than 100 x 109/L platelets and no requirements for blood transfusions). The role of dysplasia is not clear and for patients in whom dysplasia was present at diagnosis it could be useful to have also information of cytogenetic, molecular and immunophenotypic analysis. Specific characteristics could be present at the time of CR, leading to special considerations:
Complete remission with incomplete blood count recovery (CRi): It means morphological CR but without recovering neutropenia and/or thrombocytopenia. The benefit of this response is not clear
Complete remission without platelet recovery (CRp): This has been mainly reported after treatment with gentuzumab-ozogamicin (GO), and its influence on prognosis is not clearly defined.
Cytogenetic complete remission (CRc): Absence of previous clonal cytogenetics abnormalities.
Complete molecular remission (CRm): Absence of previous detected clonal molecular alterations.
6.11.3 Partial response
It refers to the same criteria of CR with a reduction of 50% of marrow blasts which are within 5% to 25%. Thus, the criterion of less than 5% marrow blasts is not achieved. If less than 5% marrow blasts are present but with Auer rods, the response should be considered as PR. PR does not imply a meaningful response but its usefulness is mainly used for detecting antileukemic activity in specific clinical trials.
6.11.4 Treatment failure
Usually, treatment failure refers to situations different from CR. This is true for general clinical management when long term survival is the primary end-point. How to manage the categories of CRi and CRp is complicated and it could be useful to complete the evaluation of these cases with the study of MRD to take clinical decisions. We also recommend to be cautious with CRp in the case of treatment with GO, so this situation could not be clearly related with bad prognosis and further studies are required. PR should be only considered for investigational purposes in early phases of clinical trial to identify antileukemic activity of a specific treatment. In a recent study from the MD Anderson presented at the 2007 ASH meeting, responses other than CR were related to a worse outcome.
6.11.5 Early blast clearance
The “speed” of the response to induction therapy, also known as “blast clearance”, is related with the prognosis both for attainment of CR and for long term survival72,275. The “blast clearance” has been studied in bone marrow seven days after induction therapy72 or by means peripheral blood cell counts275 to analyze its relation with survival. Both studies have found significant impact of this parameter in the outcome of AML patients.
6.11.6 Minimal Residual Disease
Monitoring of minimal residual disease (MRD) by flow cytometry is one of the most important prognostic factors together with cytogenetics and response to first line treatment23. It is strongly recommended on a type C basis to monitoring residual disease and to standardize flow cytometry techniques.
The main aim of induction therapy is to reduce the leukemic burden to those levels not cytologically detectable. However it is well known that a population of malignant residual cells not morphologically detectable remains after induction treatment, and virtually all patients will relapse if no post-remission therapy is applied276. This small persisting population of leukemic blasts is referred to as MRD. MRD can be studied by means of multiparameter immunophenotyping of leukemic cells by flow cytometry. This technique allows detection of residual leukemic cells with a sensitivity up to 10-4 to 10-5 (1 blast cell in 10,000 up to 100,000 nucleated cells), it could be standardized in clinical laboratories and it is applicable in 80% of patients or even up to 100% depending on the number of monoclonal antibodies used277-280. The concordance between results from flow cytometry and PCR is greater than 85%281,282.
Different clinical trials have shown that the prognosis of patients with AML is clearly influenced by the MRD level at different points. High levels of MRD are related to a high relapse probability as shown in Table 1023,281,283-290.
Table 10. MDR and relapse free survival in AML
|n.||MDR||RFS or relapse||Timing|
|San Miguel 2001; San Miguel 1997||126||< 10-4
> 10-4 – < 10-3
> 10-3 – < 10-3
|100% RFS at 3 years
|Venditti 2000||63||> 3,5 x 10-4
< 3,5 x 10-4
|Kern 2004||62||log-diff > 2,28
log-diff < 2,28
|26% RFS at 2 years
|CR and After consolidation|
|Feller 2004||51||> 1%
|33% RFS at 3 years
|Kern 2004||106||log-diff > 2,28
log-diff < 2,28
|65% RFS at 3 years
6.12 New drug therapy in AML
In the last years, a significant increase in knowledge of the biological mechanism implicated in AML has taken place. This knowledge has had a significant impact in the diagnosis and prognosis stratification of AML and it has allowed even the change of the classification of this disease. Although, the impact of this improvement in AML characterization has led to concepts of “tailored therapy”, it has not yet resulted in radical changes in the treatment of these patients. However, the basis for the development of new therapeutic strategies has been in part established.
Some new drugs resembling the standard chemotherapy, like Clofarabine or Cloretazine, have been developed and they are currently being tested in clinical trials291. Nevertheless, special interest is focused in the development of the concept known as “Target Therapy”, which is clearly related to the personalized medicine. Identification of immunological markers or molecular alterations, resulting in a variety of proteins related to the pathogenesis of AML, has served for the development of specific drugs targeting these molecules. Treatment with ATRA for the APL or imatinib for CML is a clear example of how this type of therapy could change the natural history of these diseases. New drugs targeting pathogenetic events in AML is one of the most important areas in the study of this disease and it should be known for all physicians treating AML patients, although the vast majority of these treatments remain investigational. It is strongly recommended on a type R basis to refer patients who are candidates to enter clinical trials on targeted therapy to hospitals performing these studies.
10.1. Farnesyltransferase inhibitors
Ras proteins are responsible to trigger a cascade of posphorylation events affecting survival of hematopoietic cells292. These proteins are encoded by the ras family of proto-oncogenes. Mutations and abnormal expression of ras genes resulting in an activation of ras proteins have been described in AML and could be related to its development293. Ras proteins need the addition of a farnesyl group by means of the enzyme farnesyltransferase to attach to the cell membrane for developing its function. Farnesyltransferase inhibitors were developed to avoid farnesylation of the ras proteins. Table 11 summarizes the results of some clinical trials on the use of the farnesyltransferase inhibitor tipifarnib294-296. Antileukemic activity has been observed in different groups of AML patients but further investigations are needed to establish the role of this treatment in AML and a report from a large randomized study presented at the 2007 ASH meeting did not show any advantage of this drug in older patients. Some genes like RASGRP1, APTX or AKAP 13 have been shown to be predictive for response to tipifanib297,298.
6.12.1 Antisense oligonucleotides
Overexpression of the antiapoptotic protein bcl2 has been shown in patients with AML and it is related to a bad prognosis299,300. This abnormal expression of bcl2 protein could be related with chemoresistance by means of alterations in the caspase- and non caspase-mediated apoptosis. To reduce the apoptotic threshold and increase the response to chemotherapy, G3139 (oblimersen sodium) has been used in the treatment of AML (Table 12)301-303. Data from these trials show the feasibility to combine G3139 with chemotherapy, but no solid conclusions about its efficacy can yet be made.
6.12. 3. Hypomethylating drugs
Epigenetic changes in the DNA of some genes, including methylation or histone deacetylation, have been described in AML and represents an interesting target for drug development304-306. Although only prelimary results are available deriving from phase I-II clinical trials, the same suggest a significant antileukemic activity when decitabine (a hypomethylating agent) is used for the treatment of AML, alone or in combination with histone deacetylase inhibitors (Table 13)307-309.
6.12.4 FLT3 inhibitors
The FMS-like tyrosine kinase receptor (FLT3), also known as stem cell kinase (STK1), belongs to the class III kinase receptors, like c-kit, PDGF-R or c-fms. It is mainly expressed by the hematopoietic progenitors cells and it plays an important role in proliferation and differentiation310,311. Activation of the FLT3 receptor results in the induction of cell signaling pathways that regulates proliferation and apoptosis and it is related to an increase in the proliferation of AML cells82,312. Mutations of FLT3, mainly internal tandem duplications and to a lesser extent point mutations at the Asp 835, have been described in AML patients resulting in an activation of the receptor82,312-315. Intensive research has been conducted to develop FLT3 tyrosine kinase inhibitors that have been used in different phase I-II clinical trials (Table 14)316-323. Although they have shown antileukemic activity, reported responses mainly consisted on a reduction in the blast cell counts, with few cases of CR. It is interesting that some of these kinase inhibitors also display activity against other kinase molecules rather than FLT3, including VEGR-2.
6.12.5 Multidrug resistance modulators
Overexpression of the P-glycoprotein, encoded by the MDR1 gene, is not uncommon in AML, mainly in older patients, unfavorable cytogenetics or after relapse and it is related with chemoresistance. So, the use of multidrug resistance modulators could enhance the effect of chemotherapy. Table 15 summarizes clinical trials on the use of P-glycoprotein modulators. With the exception of one randomized clinical trial using cyclosporine, no clear benefit form the use of such treatment can be observed in phase III randomized clinical trials and this approach also remains investigational253,324,325.
Bortezomib is a proteasome inhibitor with clinical activity in hematologic malignancies. Leukemia stem cells have elevated levels of the active form of nuclear factor-κB which have antiapoptotic activity and may be related with chemoresistance. In addition, proteasome activity increases in leukemia cell lines after treatment with chemotherapy. Both, nuclear factor-κB and proteasome could be targeted with a proteasome inhibitor like bortezomib. Although this strategy seems interesting, available data come from preliminary studies (Table 16)326,327. When used as mono therapy, only a reduction of leukemic blast has been described 326. Using in combination with chemotherapy it could be only concluded that the treatment is feasible, but efficacy remains to be investigated327.
6.12.7 Gemtuzumab Ozogamicin
Gentuzumab Ozogamicin (GO) is a humanized immunoglobulin (IgG4) derived from a mammalian myeloma cell line and directed against the CD33 antigen in hematopoietic cells328,329. This monoclonal antibody is chemically linked to a potent antitumour antibiotic, calicheamicin, which is released into the cell after interaction of GO and CD33. This allows to use this drug while its effects on other organs rather than the hematopoietic system are limited. GO is approved by the Food and Drug Administration for the treatment of AML in first relapse in patients aged 60 years or older. Several studies have been conducted to study the efficacy and safety of GO, both in older and younger patients255,330-341. Some of these studies are summarized in Tables 17, 18 and 19. GO administered as a single agent is able to achieve around 15% CR rate in relapsed patients. One of this studies has opened the possibility to investigate GO in combination with standard chemotherapy as a first line treatment for AML336. This study suggests that the combination of standard chemotherapy and GO at 3 mg/m2 is safe and highly effective. Randomized trials are being performed to confirm these data. The use of GO has been related to the development of sinusoidal obstruction syndrome (SOS), mainly for patients undergoing HSCT after treatment with GO 342-344. This risk could be lower if the transplant is performed two or three months after receiving GO.
Table 11. Clinical trials on farnesyltransferase inhibitors
|Karp||2001||I||R115777 (Tipifarnib)||Farnesyltransferase inhibitor||
Aged more than 18 years
6 newly diagnosed poor prognosis
|32% (8 of 25)6 PR2 CR|
Median age 74 years
|Untreated||23%14% CR9% PR or improvement|
Median age 62 years
|Refractory or relapsed||4% CRs or CRpFor CR or CRp median survival 369 days|
Table 12. Clinical trials on antisense oligonucleotide (Bcl-2 antisense)
|Bcl-2||17 AML||Relapsed or refractoryAged more than 18 years||47% (8 of 17)6 CR2 CRi|
|Marcucci||2005||I||G3139 + DA inductionG3139 + HiAC consolidation||Bcl-2||29 AML||Untreated≥ 60 years||48%Relapse 50% with a median follow-up of 12 months|
≥ 60 years
|25% (12 of 48)5 CR7 CRp|
Table 13. Clinicals trials on hypomethylating drugs
|Issa||2004||I||Decitabine||Epigenetic changes (hypomethylation)||
Median age 60 years
|Relapsed and refractroy||Relapsed and refractroy
14% CR8% PR
Epigenetic changes (hypomethylation)
|48 AMLMedian age 60 years||Untreated and relapsed||8% PR
19% in AMLIncluding CR and CRp
Decitabine + Valproic acid
Epigenetic changes (hypomethylation)
|25 AMLMedian age 70 years||Untreated and relapsed||44% (11 of 25)4 CR4 CRi3 PR|
Table 14. Clinical trial on FLT3 inhibitors
|Giles||2003||II||SU5416||VEGR-2, c-kit, FLT3||
Median age 64 yrs
|Relapsed and refractory||
1 Hematologic improvement
|Fiedler||2003||II||SU5416||VEGR-2, c-kit, FLT3||43 ML||Refractory or elderly unfit||
Median age 67 yrs
|Mainly previous treated||5 decreases in blast counts|
|Smith||2004||I-II||CEP-701||FLT3 (others)||14 AML||Relapsed and refractory||5 decreases in blast counts|
|Stone||2005||II||PKC412||FLT3 (others)||19 AML||
Relapsed and refractory
14 decreases in blast counts
6 > 50% reduction
|Fiedler||2005||I||SU11248||FLT3 (others)||15 AML||Refractory||6 morphologic or partial responses|
|Knapper||2006||II||CEP701||FLT3 (others)||27 AML||Untreated older patients||8 transient reductions in blast counts|
Median age 70 yrs
|High risk||2 decreases in blast counts|
Table 15. Clinical Trials on Multidrug Resistance Modulation
DR + HiDA
|Relapsed, refractory, secondary, high risk and blast CML crisis||49% CR or return to chronic phase|
Ara-C + MTZ + VP16
|P-glycoprotein modulator||23 AML||Relapsed or refractory||26% CR|
PSC833 + ADE (ADEP)
|Untreated||46% CR for ADE vs. 39% CR for ADEP
DR + Ara-C
|De novo and relapsed||11 CR1 PR|
PSC833 + ADE (ADEP)
Aged less than 60 years
|Untreated||78% CR ADE vs. 73% CR ADEP
Similar OS and better DFS for ADEP
In patients aged 45 or younger better OS and DFS with ADEP
|van der Holt||2005||III||
PSC833 + DR + Ara-C
DR + Ara-C
Aged 60 years or older
CR 54% vs 48%
5y EFS 7% vs. 8%
DFS 13% vs. 17%
Table 16. Clinical trials on Bortezomib for AML
|Cortes||2004||I||Bortezomib||Proteasome Inhibitor||15 AML||Relapsed or refractory||
4 decreases in blast counts
1 improvement on neutrophils
IDA + Ara-C
MAedia age 62 yrs
|Relapsed and untreated||
Table 17. Examples of Clinicals Trials on GO in AML older patients (I)
|Author||N||Median Age||Disease Status||Schedule||CR AND CRp||Survival|
|Amadori||57||68 (61-73)||First line||Sequential GO 9 mg/m2 two doses followed by MICE||35,1% after GO
54.4% after MICE
|1-year OS 34%
RFS 190 days
First line in patients aged 75 years
or between 61 and 75 years with PS WHO grade 2
|Two doses of GO 9 mg/m2
Two additional doses if CR
|17% (33% between 61 and 75 years
and 5% aged 75 or more years)
|1-year OS 34% and 2-year OS 7%
Median OS 11,4 months for patients between 61 and 75 years and 1 month for those aged more than 75
(37 AML and 14 MDS)
|71 (65-89)||First line in AML and MDS||GO 9 mg/m2 days 1 and 15 (22 patients) or 1 and 8 (29 patients)
Randomization to IL-11
|22% (8% without IL-11 and 36% con IL-11)||Median OS 3 months|
|Larson||101||69 (60-87)||Untreated first relapse||GO 9 mg/m2 two doses in a 14 days period
80% received two or more doses
Related to duration of first remission
|Median OS 5,4 months
OS 14,5 y 11,8 months for RC and RCp patients
Median RFS 3,3 months
Table 18. Examples of Clinicals Trials on GO in AML older patients (II)
|Author||Treatment Related deaths||Median Days of Neutropenia||
Increase in Transaminases
Increase in Bilirubin
|Amadori 2004||5,3% afetr GO
|37 days since first GO administration||5,3 % after GO||8.8% after GO||3 cases (5.3%) alter GO and 2 cases after MICE|
|Amadori 2005||17% (all of them older than 75 years)||28 days since first GO for CR patients||10%||10%||2,5%|
|Larson 2002||5% (5 patients)
9 patients died during treatment because disease progression
|42 days since first GO for RC and RCp patients||15%||24%||0% (5 pacientes developed ascitis)|
Table 19. Examples of Clinicals Trials on GO in AML younger patients
|Author||n||Age||Disease status||Schedule||CR and CRp||Survival||
Increase in bilirubin
Increase in AST/ALT
|Arceci 2005||29||12 (1-16)||Untreated relapse or refractory||6-9 mg/m2 two doses||28%||2 patients alive in CR at +645 and +112||7%||21%||1 patient after GO|
|Kell 2003||64||(17-59)||First line||QT + GO different doses||84%
91% with FLAG or DA
|78% at 8 months with FLAG or DA||29% liver toxicity||7 cases (all receiving thioguanine)|
|Sievers 1999||40||54 (24-73)||Relapse or refractory||GO different doses||5 of 40 (3 CR and 2 CRp)||—–||—–|
|Van der Heiden 2006||38||58 (27-77)||17 relapse
15 first line
|19 with GO
19 with GO + QT
|22% CR and CRp
60% in first line non secondary AML
|Larson 2005||overall||270||61 (20-87)||First relapse||GO 9mg/m2 dos dosis en 14 días||26%||OS 12,2 months for CR and 12,9 months for CRp|
|< 60||120||47 (20-59)||First relapse||GO 9mg/m2 two doses in a 14 days period||28%||OS 17,2 months for CR and 18,4 months for CRp|
6.13 Acute Promyelocytic Leukemia
Acute promyelocytic leukemia (APL) is a relatively uncommon hematologic malignancy with an estimated 600 to 800 newly diagnosed cases per year at the US350. APL is very rare in children aged less than 10 years and its incidence increases steadily during the teen years, reaches a plateau during early adulthood, and remains constant until it decreases after age 60 years351. In contrast, other subtypes of AML have an exponential increase after age 55 years. Several factors have been suggested to be associated with the risk of developing APL, mainly exposure to chemotherapy (particularly drugs targeting topoisomerase II) or radiotherapy, particularly in patients with a history of breast cancer352-354. Regarding the incidence of APL among ethnic groups, contradictory data particularly referred to a presumed higher incidence of APL in “Latinos” have been reported in the literature355,356. Therefore, this epidemiologic issue is still a matter of controversy and deserves additional investigation.
Because the efficacy of differentiation treatment based on retinoids and/or arsenic derivatives is strictly dependent on the presence of the PML/RARA fusion in leukemia cells, genetic confirmation of this specific lesion is a mandatory standard in all cases. Morphological diagnosis of hypergranular (typical) APL is highly predictive of an underlying PML/RARA rearrangement, and immunophenotyping by multiparameter flow cytometry can improve the accuracy of diagnosis and it is recommended on a type C basis357,358, particularly in patients with morphologic features evoking a microgranular (variant) subtype. However, patients with morphologic and/or immunophenotypic features suggestive of APL without the PML/RARA rearrangement, and vice versa, have been described in the literature359-361.
6.13.3 Morphology and Immunophenotyping
A marrow aspirate is considered a mandatory standard. This may be omitted only when the peripheral blast count is high and the patient is to be considered for palliative treatment only. A trephine biopsy is required only in the case of a dry tap in the absence of abnormal cells in the peripheral blood to allow a morphological and molecular diagnosis. As a standard, morphological studies of the bone marrow slides require a Romanowsky-derived stain, such as Wright, Wright-Giemsa or May-Grunwald Giemsa stains, usually complemented by myeloperoxidase or Sudan black B stain.
Immunophenotyping by multiparameter flow cytometry can increase the accuracy of a morphologic suspicion of PML/RARA-positive APL and it is a standard recommended on a type C basis. Typically, PML/RARA-positive leukemia blasts show immunophenotypic features that are similar to those of normal promyelocytes (CD34–/+ heterogeneous, CD117–/+ dim, HLADR–/+ dim, CD13+/++, CD11b–)357; however, unlike their normal counterpart, PML/RARα-positive promyelocytes display abnormally low levels of CD15 (CD15–/+ dim versus CD15+++)357,358. Blasts of the hypogranular variant form of APL (M3v) frequently coexpress the T-lineage affiliated marker CD2 with myeloid markers CD13 and CD33362-364.
6.13.4 Genetic and Molecular Diagnosis
Confirmation of genetic diagnosis is a mandatory standard and should be performed, if possible, on leukemia cells from bone marrow. The identification of the APL-specific genetic lesion in leukemic cells is feasible at chromosomal, DNA, RNA, and protein levels, respectively, with the use of conventional karyotyping, fluorescence in situ hybridization (FISH), reverse transcriptase polymerase chain reaction (RT-PCR), or anti-PML monoclonal antibodies.
All the aforementioned options are equally specific but not equally reliable methods to confirm the genetic diagnosis of APL. In particular, cytogenetics is much less efficient than the others. In terms of rapidity, specificity and sensitivity, FISH and immunostaining with anti-PML monoclonal antibodies are highly efficient to confirm the diagnosis of APL. However, these techniques should not replace RT-PCR, which allows definition of the type of PML-RARA isoform and the target for MRD evaluation.
Karyotyping on G-banded metaphases obtained from bone marrow samples is usually performed by conventional methods on direct, 24 hr and 48 hr cultures. Although, highly specific, cytogenetic analysis is expensive, very time-consuming, needs good quality metaphases (lacking in up to 20%), and by definition fails to detect cases where the PML-RARA fusion results from cryptic rearrangements (false negatives). In addition, secondary chromosomal abnormalities seem not to have significant prognostic value in APL365,366. However, cytogenetics is potentially useful in the characterization of cases lacking the PML-RARA fusion. This may facilitate identification of rarer molecular subtypes of APL including those with t(11;17)(q23;q21), t(11;17)(q13;q21) and t(5;17)(q35;q21) leading to PLZF-RARA367, NuMA-RARA368 and NPM1-RARA369 fusions, respectively, as well as others more recently described370-372.
FISH analysis of PML/RARA can be carried out using standard methods and commercially available fluorescently labelled probes. Although in some cases peripheral blood samples are suitable for study (in particular when hyperleukocytosis is present at diagnosis), FISH is preferably performed in bone marrow samples. The protocol for FISH detection of PML/RARA has been reported in detail by Grimwade et al.373. This methodology is highly specific and sensitive, and much less expensive and time-consuming than karyotyping. However, it is important to recognize the potential limitations of some probe sets used for molecular diagnostics. In particular, those that specifically detect the RARA-PML fusion gene on der(17) will not show fusion signals in the presence of non-reciprocal rearrangements where RARA-PML is deleted or where PML-RARA is formed as a result of an insertion. Small PML-RARA insertions can also be missed by FISH when using very large probes; in such cases it is more appropriate to use relatively small cosmid probes360. FISH provides no information about the isoform of PML/RARA, which is required for molecular monitoring of minimal residual disease. However, FISH can be useful in the investigation of suspected APL cases that lack a PML-RARA fusion, using RARA probes that span the breakpoint region to investigate for evidence of a RARA rearrangement, facilitating the identification of the fusion partner.
RT-PCR analysis of PML-RARA is preferably carried out on RNA extracted from bone marrow samples, although the fusion transcript is usually readily detectable in peripheral blood even in cases presenting with leucopenia. Standardized RT-PCR assays for detection of the PML-RARA fusion were established within the Biomed-1 Concerted Action374. RT-PCR probably provides the gold standard approach for confirming a diagnosis of APL. In addition to its high specificity and sensitivity, it is essential for defining PML breakpoint location thereby establishing the target for reliable monitoring of minimal residual disease (MRD). However, poor RNA yield (false negative), contamination and artifacts (false positives), and the relatively long turnaround time (~2 days) are the main drawbacks of this methodology. In addition, it is advisable that diagnostic and monitoring samples are analyzed in reference laboratories by well-trained personnel with considerable expertise in RT-PCR for PML-RARA.
Immunostaining with anti-PML monoclonal antibodies on dry smears of bone marrow or peripheral blood (providing circulating blasts are present) is helpful to achieve a rapid diagnosis. This technique is highly specific for presence of an underlying PML-RAR fusion protein375-378, indicated by a microspeckled staining pattern (>30 nuclear dots) in the nuclei of leukemic cells with the PML antibody, which detects both PML-RARα and the normal PML protein. The test will also be positive in those rare cases where atypical breakpoints occur within the PML locus, which could potentially be missed by standard PCR primers. In normal cells and blasts from other subtypes of leukemia (including APL molecular variants e.g. PLZF-RARA and NPM1-RARA) a wild-type PML staining pattern is observed with discrete nuclear dots (typically <20/nucleus) that relate to organelles known as “PML nuclear bodies”360,361. Either indirect immunofluorescence or immunohistochemistry may be used. Results from the immunofluorescence assay can be achieved in only 2 hours. In light of its very convenient cost-benefit ratio, the assay is highly recommended to rapidly confirm the diagnosis of APL effectively identifying patients with the PML-RARα fusion, thereby predicting those likely to respond to molecularly targeted therapy with ATRA or ATO. This test is particularly valuable in small centers lacking access to a molecular diagnostics laboratory and in cases in which RNA is not available to confirm a diagnosis.
6.13.9 Sample processing and banking
A specific recommendation for sample banking of all AML cases at diagnosis has been made in the revised criteria for AML diagnosis and outcome evaluation274. The laboratory that will assume the responsibility for sample banking (recommended), confirmation of diagnosis at the genetic level, and monitoring MRD by RT-PCR, should receive samples as follows:
For FISH or immunostaining studies, 3-4 bone marrow smears and 3-4 peripheral blood smears at diagnosis are required. Samples can be sent at ambient temperature. Smears that are not used immediately must be stored for banking at –20 °C covered by aluminum paper.
For RNA extraction and RT-PCR analysis of PML-RARA, one bone marrow aspirate vial (2-3 ml) and one peripheral blood vial (20-30 ml), both in sodium citrate or EDTA, are required. Samples should be processed within 24 hours. Isolated mononuclear cells in guanidium isothiocyanate can be stored for banking at – 20 °C.
For conventional karyotyping and FISH studies, bone marrow aspirate (1-2 ml) should be collected in heparin and dispatched at ambient temperature. Samples will be processed on arrival for these diagnostic studies and pelleted nuclei fixed with methanol and acetic acid (3:1) can be stored at – 20 °C.
6.13.10 Other genetic studies
Mutations in the gene encoding the fms-like tyrosine kinase 3 (FLT3) are more frequently seen in APL than in other subtypes of AML379. However, although FLT3 mutations are associated with a higher white blood cell (WBC) count at presentation, they do not add to the specific diagnosis of APL, do not influence management, nor do they furnish important independent prognostic information380,381. Therefore, the inclusion of the analysis of these mutations in the routine work up of APL is not recommended on the basis of current evidence. Although APL has a characteristic gene expression signature on microarray59,382, and this may provide a useful additional diagnostic tool in the future, for the time being this approach remains in the research arena
6.14 Treatment of newly diagnosed patients
6.14.1 APL as a medical emergency
Definitive diagnosis of APL requires the confirmation at the genetic level. However, due to the high risk of early death in these patients, if APL is suspected on the basis of morphological14,383 or immunological studies, or by the presence of severe coagulopathy, it is strongly recommended on a type R basis to start both differentiation and supportive therapy before the results of genetic tests are available.
6.14.2 Starting ATRA
ATRA is known to improve the biological signs of APL coagulopathy rapidly; hence early initiation of this agent is likely to decrease the risk of severe bleeding. For this reason, treatment with ATRA should be initiated without waiting for genetic confirmation of the diagnosis, preferably the same day that diagnosis is suspected. For patients presenting with low WBC count, administration of appropriate chemotherapy may be delayed until the genetic diagnosis is confirmed; however, in patients with hyperleukocytosis (e.g. WBC >10 × 109/L), due to the high risk of induction death and differentiation syndrome, chemotherapy should be started without delay even if the molecular results are still pending.
6.14.3 Initial management of coagulopathy
Intracerebral and pulmonary hemorrhages are the most frequent causes of early induction deaths and they also occur before diagnosis has been made and therapy started, while the characteristic coagulopathy of APL is active. The US Intergroup384 and the PETHEMA group385 have reported around 5% of patients considered not eligible for induction therapy due to very poor clinical condition (ECOG performance status greater than 3), mostly due to lethal or life threatening hemorrhages before starting therapy386. It is reasonable to recommend on a type C basis that supportive measures to counteract the coagulopathy should be instituted immediately the diagnosis of APL is considered and consist of fresh frozen plasma, fibrinogen and platelet transfusions to maintain the fibrinogen concentration and platelet count above 100-150 mg/dL and 30 – 50×109/L, respectively; such replacement therapy should continue during induction therapy until disappearance of all clinical and laboratory signs of coagulopathy. These measures should be more aggressive in patients with a higher risk of hemorrhagic mortality because of active bleeding387 or laboratory signs of coagulopathy385,388. Patients at a greater risk of fatal hemorrhage are those presenting with increased WBC389,390 or peripheral blast385,387 counts, signs of coagulopathy385, abnormal levels of creatinine385, or poor performance status388.
It is recommended on a type R basis to avoid central venous catheterization and lumbar puncture before and during remission induction therapy due to high risk of hemorrhagic complications until coagulopathy has resolved. The routinely use of heparin, tranexamic acid, or other anticoagulant or antifibrinolytic therapy to attenuate the hemorrhagic risk is not recommended on a type C basis. These measures remain as investigational. There are case reports of the use of recombinant factor VIIa in the situation of severe life-threatening hemorrhage, but it should be used only on an individual basis or into investigational studies391,392.
6.14.4 Specific treatment
The simultaneous administration of ATRA and anthracycline-based chemotherapy is currently considered the standard induction treatment in newly diagnosed patients with APL, leading to complete remission (CR) in 90 to 95% of patients387,389,390,393. These data indicate that virtually all PML-RARA positive APLs are sensitive to ATRA and anthracycline-based chemotherapy. Two randomized trials of the European APL group394 and the North-American Intergroup384, showed that patients receiving ATRA followed by chemotherapy had significantly better outcomes as compared to patients treated with chemotherapy alone. A later randomized clinical trial showed that results were improved given ATRA and chemotherapy simultaneously, rather than sequentially389. It has been confirmed in other large multicenter trials390,393,395-398. ATRA and chemotherapy simultaneously given is recommended as the standard induction treatment for newly diagnosed APL patients on a type 2 evidence. Exceptions to the use of the standard approach should be considered only for individual cases in which chemotherapy is contraindicated (eg, severe organ failure, anticoagulant therapy, patients older than 80 years, and others), as well as in cases in which alternative options for induction therapy are dictated by socioeconomic factors or clinical trial design. However, modifications to the standard approach based on the presence of leukemia cell characteristics that have variably been considered to predict a poorer prognosis (eg, secondary chromosomal abnormalities, FLT3 mutations, CD56, and BCR3 PML-RARA isoform) are not supported by the available data.
The standard consolidation for APL includes ATRA and anthracyclines. The benefit provided by the addition of ATRA to chemotherapy for consolidation has not yet been demonstrated in randomized studies. Nevertheless, historical comparisons of consecutive trials carried out independently by the GIMEMA399 and PETHEMA393 groups showed a statistically significant improvement in outcomes when ATRA at standard dose (45 mg/m2/d for adults; 25 mg/m2/d for children) was given for 15 days in conjunction with chemotherapy, suggesting that ATRA contributes to reduction in relapse risk. The use of ATRA in consolidation therapy is recommended on a type C basis.
A tailored strategy for consolidation adapting treatment intensity according to predefined risk factors for relapse, particularly presenting WBC and platelet count is recommended on a type R basis400.
Contradictory data regarding the use of ATRA-based post-consolidation therapy have been reported in four randomized studies, ranging from treatment benefit to poorer survival384,389,401,402. Both studies not demonstrating clinical efficacy of maintenance tested negative for PML/RARA at the end of consolidation. No conclusive evidence exists as to whether ATRA-based maintenance therapy should be used when molecular remission is achieved at the end of consolidation.
6.14.5 Controversies in the first line treatment of APL
As to the type of anthracycline and whether it should be combined with other chemotherapy agents, both issues still remain controversial; at least as far as induction therapy is concerned. Comparable CR rates have been reported using ATRA plus daunorubicin and cytarabine389,403 and ATRA plus idarubicin alone395,397, with no apparent advantage observed by adding other cytotoxic agents390. The only randomized trial reported so far404 was unable to demonstrate differences in terms of CR and induction failure rates when comparing daunorubicin alone versus daunorubicin plus cytarabine for induction therapy. However, this study demonstrated an increased risk of relapse when cytarabine was omitted from both induction and consolidation therapy. A preliminary result of a second randomized trial has recently been reported which compared ATRA with idarubicin against ATRA with daunorubicin and cytarabine. There was no overall difference in response, relapse or overall survival but a small increase in deaths in remission was noted in the cytarabine containing arm405. With respect to the type of anthracycline, idarubicin has shown a slight survival advantage when compared with daunorubicin in conjunction with cytarabine only in younger AML patients406. In APL, no prospective studies have been conducted to assess the comparative value of both anthracyclines.
The role of cytarabine in APL remains controversial. A recent randomized study by the European APL group404 reported an increased risk of relapse when cytarabine was omitted from a schedule including daunorubicin. Whether the particular choice and dose of anthracycline chemotherapy used could be responsible for these results is uncertain. A joint analysis of the PETHEMA and the European APL groups407 demonstrated better RFS for younger patients (10 × 109/L)399. This fact has not been observed in joint analysis of the PETHEMA and GIMEMA group studies that used identical type and dosage schedules of anthracyclines or in the preliminary results of the MRC15 trial400,408. The addition of cytarabine could be useful in patients younger than 60 years with WBC counts higher than 10 × 109/L on a type C basis, although no difference in overall survival has been demonstrated.
In last years ATO has emerged as an alternative approach. After its use for the treatment of relapsed patients with APL409,410, first line treatment has been investigated showing a CR rate from 86 to 95%411-414. However, it should be noted that ATO was combined with ATRA, chemotherapy or gemtuzumab ozogamicin in a variable proportion of patients, particularly those presenting with hyperleukocytosis. The use of ATO as first line treatment remains investigational, ideally in the setting of clinical trials with appropriately designed comparisons with the standard ATRA plus anthracycline chemotherapy approach in terms of efficacy, safety, and cost-effectiveness. In the meantime, the use of ATO should be restricted to patients included in clinical trials or for those in whom chemotherapy is contraindicated.
A large randomized study has explored the addition of ATO to standard consolidation showing a better outcome for patients treated with this schedule403. However, the overall survival for the control group in this study was lower than that reported in other series using ATRA and anthracycline chemotherapy-based schedules. The results in the pediatric age group in the US Intergroup study were particularly disappointing when compared with other standard approaches415-418.
Hematopoietic stem cell transplantation
The high cure rate obtained using upfront ATRA and chemotherapy indicates that there is no role for routine use of HSCT for patients who are in the first molecular remission at the end of consolidation and this procedure is not recommended on a type C basis for these patients. There is a small fraction of patients with persistent minimal residual disease at this time-point resulting in a poor prognosis419. For these patients, allogeneic HSCT is recommended on a type R basis if a suitable HLA-matched donor is available. Additional therapy such ATO could be considered in these cases to reduce disease burden and ideally achieve molecular CR prior to transplant. For patients not having a suitable HLA-matched donor or those who are unfit for ablative conditioning it is recommended on a type R basis to receive investigational approaches like ATO or GO. Provided that the patient achieves molecular CR in the marrow and has a PCR negative harvest autologous HSCT can be considered as consolidation therapy. Although good results have been achieved using this approach420,421 the role of transplant is uncertain, since it is possible that long-term remissions can also be achieved with multiple courses of ATO and/or GO.
6.14.6 Management of specific targeted treatment complications
Prevention and management of differentiation syndrome
The differentiation syndrome is related to the treatment with ATRA or ATO and it should be suspected clinically in the presence of one of the following symptoms and signs: dyspnea, unexplained fever, weight gain, peripheral edema, unexplained hypotension, acute renal failure or congestive heart failure, and particularly by a chest radiograph demonstrating pulmonary infiltrates, or pleuropericardial effusion. Due to the life-threatening nature of the full-blown syndrome, and in spite of the not pathognomic nature of any of these symptoms, it is recommended on a type R basis to start specific treatment with dexamethasone at a dose of 10 mg twice daily by intravenous injection at the very earliest symptom or sign. Temporary discontinuation of ATRA or ATO is indicated only in case of severe differentiation syndrome or lack of response to dexamethasone. If a favorable response is obtained, dexamethasone should be maintained until complete disappearance of symptoms, and then ATRA or ATO should be resumed. Preemptive therapy with dexamethasone is the standard approach to treat patients developing differentiation syndrome. No clear evidence on the efficacy of prophylaxis is available, although data from uncontrolled studies suggest that it could be useful in patients presenting with WBC count greater than 5 × 109/L393,422.
Prolonged QT Interval Associated with ATO
Treatment with ATO is associated with several electrolyte abnormalities and prolongation of the QT interval which require careful monitoring423. Maintenance of the serum potassium above 4.0 mmol/L (4.0 mEq/L) and serum magnesium above 0.82 mmol/L (2.0 mg/dL), well above the lower limit of normal, is indicated. For patients with a heart rate of greater than 60 beats per minute, if the QTc (heart rate corrected) interval is prolonged longer than 500 millisecond, ATO should be withheld, the electrolytes repleted (potassium and magnesium), and other medications that may cause prolonged QTc interval searched for and ideally discontinued. For patients with a heart rate of 60 beats per minute or less, the absolute QT (uncorrected for the heart rate) interval can be used. In addition to prolongation of the QT/QTc interval, approximately 13% of patients treated with ATO may develop hypokalemia or hyperglycemia. Once the QT/QTc returns to approximately 460 milliseconds, and the electrolytes are repleted, ATO may be resumed.
6.14.7 Other supportive measures
Management of coagulopathy has been described before. General supportive care aspects in APL, the use of antibiotics, hematopoietic growth factors, prevention of tumor lysis syndrome, and transfusion policy, including red cell, granulocyte, and platelet transfusions (once the coagulopathy is under control), do not differ from those applied in patients with other subtypes of AML273. Leukapheresis is not recommended on a type R basis as part of initial therapy for APL patients presenting with elevated WBC, since this procedure may exacerbate the coagulopathy and was associated with a high risk of induction death in one series424. Early institution of chemotherapy in combination with ATRA accompanied by prophylactic steroids is the standard treatment approach in this life-threatening situation. Hyperleukocytosis related to treatment with ATO can be managed with careful observation, checking in particular for evidence of emerging differentiation syndrome. Hydroxyurea could be considered.
The central nervous system (CNS) is the commonest site of extramedullary disease in APL and at least 10% of hematologic relapses are accompanied by CNS involvement425. Therefore, the possibility of CNS disease should be considered in any APL patient with neurological symptoms and be excluded in patients subject to relapse. Because the majority of CNS relapses occur in patients presenting with hyperleukocytosis426, some strategies include CNS prophylaxis after attainment of CR for patients in this particular high-risk setting. For patients without hyperleukocytosis, in whom the risk of CNS relapse is extremely low, there is a general consensus to avoid CNS prophylaxis.
6.15 Assessment of response
6.15.1 Assessment of induction response
Delayed differentiation of blasts, which is occasionally up to 40-50 days after treatment, can result in a misinterpretation of morphologic and cytogenetic studies. As discussed above, CR is attained in virtually all patients with genetically proven PML-RARA APL. For this reason, in case of any doubt about the achievement of CR, it is recommended on a type R basis to repeat another bone marrow (BM) assessment after an additional interval of 2-3 weeks while keeping the patient on ATRA, and meanwhile refrain from new therapeutic interventions. Since the introduction of this strategy, no cases of resistant leukemia have been recorded among the last 350 patients enrolled in the PETHEMA studies385.
Molecular assessment by RT-PCR on regeneration following induction has no clinical relevance, and clinicians should refrain from making therapeutic decisions on the basis of results at this time point.
6.15.2 Molecular assessment at the end of consolidation and beyond
Molecular remission after the final course of chemotherapy is a major treatment goal because molecular MDR at this point is extremely relevant to determine the relapse risk in the individual patient361,427. It is strongly recommended on a type C basis to study MDR at this time-point by means of conventional nested RT-PCR or real-time quantitative PCR, although the later has significant advantages428. For patients testing PCR positive at any stage following completion of consolidation, it is recommended on a type C basis that a bone marrow is repeated for MRD assessment within 2 weeks and that samples are sent to the local laboratory, as well as to a reference laboratory for independent confirmation. It is now accepted that patients with persistent or recurrent disease at the molecular level confirmed in two consecutive low-sensitivity assays after completion of consolidation will invariably relapse unless additional therapy is given419,429. Sequential MRD monitoring (by 3-monthly BM assessment with assays achieving sensitivity of 1 in 104) after completion of therapy to allow early treatment intervention is recommended on a type C basis.
6.16 Management of relapse
6.16.1 Molecular and Hematological Relapse
Relapse can occur at the molecular or hematological level. It is recommended on a type C basis to treat patients that develop molecular relapse before frank hematologic disease is present430,431, and this treatment should be started promptly because of the kinetics of the disease can be relatively rapid432.
It is recommended on a type C basis that induction treatment for APL relapsed patients should be based on the use of ATO which have a high antileukemic activity in this setting433. The administration of at least two cycles could lead to a CR rate up to 80%434-443. Consolidation after ATO induced second CR should be considered taking into account the duration of first CR and the molecular status of the patient, although some evidence suggests that treatment intensification with HSCT444 or chemotherapy441 may improve outcomes. Options include continued treatment with repeated cycles of ATO, the use of standard chemotherapy in combination with ATRA and/or ATO, and HSCT. Regarding autologous or allogeneic HSCT, the former could be a reasonable option for patients without MRD and prolonged first CR (more than 1 year). By contrast, allogeneic HSCT could be recommended on a type R basis in patients failing to achieve a second molecular remission and for those with short first CR duration433. Patients unfit to proceed to HSCT, are candidates to repeated cycles of ATO with or without ATRA/standard chemotherapy or for an individual use of gemtuzumab ozogamicin, a drug which merits special investigational approaches in relapsed APL445,446.
6.16.2 CNS and other extramedullary relapses
Up to 3% to 5% of patients with APL experience an extramedullary relapse and in 1 of 10 APL relapses CNS is involved, which allows to recommend on a type R basis to consider it in patients subject to molecular or hematologic relapse (96-98). Experience on the management of CNS relapse is scarce, but arising from data of other leukemias it is recommended on a type R basis induction treatment of CNS relapse with weekly triple intrathecal therapy (ITT) containing methotrexate, hydrocortisone, and cytarabine until complete clearance of blasts in the cerebrospinal fluid (CSF), followed by 6-10 more spaced out ITT treatments as consolidation. Since CNS disease is almost invariably accompanied by hematologic or molecular relapse in the marrow, systemic treatment should also be given and timing should be establish on an individual basis. Chemotherapy regimens with high CNS penetrance (e.g. high dose cytarabine) have been used in this situation and in patients responding to treatment, allogeneic or autologous transplant should be the consolidation treatment of choice including appropriate craniospinal irradiation. In case of granulocytic sarcoma, wherever it is localized, radiation and intensive systemic therapy might be considered.
6.17 Summary of special situations on APL
6.17.1 Older patients and patients with severe comorbidities
APL is relatively uncommon in older patients and usually it presents with low-risk features as compared with younger patients447. Responsiveness to induction treatment and relapse are comparable to those observed in younger patients using conventional ATRA with reduced intensity chemotherapy427,447. However, the main problem is the treatment related toxicity with deaths in CR ocurring in up to 19% of patients447. Although available data are limited, for patients unfit to receive chemotherapy, ATO with or without ATRA seems a reasonable approach.
Similar approach could be used for patients with severe comorbidities that preclude the use of chemotherapy. These patients could be treated with combinations of ATO, ATRA or GO414.
APL accounts for 4% to 8% of pediatric AML in the United States (100) and compared to the disease in adults, it more frequently presents with hyperleukocytosis447. Using standard approaches with ATRA and anthracycline-based chemotherapy is the standard of treatment415-418. Standard dose of ATRA in children and adolescents is 25 mg/m2 per day448. However, the concern regarding the use of high dose of anthracyclines and their potential long-term cardiac toxicity has been the base for investigational approaches reducing anthracyclines dose (with not encouraging results)403 or using other therapeutic drugs, like ATO449,450. These approaches remain investigational.
Like adults, there is not evidence to recommend CNS prophylaxis in children. Headache is common during the treatment with ATRA and differential diagnosis should be made with pseudotumor cerebri (PTC), CNS leukemia or bleeding. The diagnosis of PTC is based on increased intracranial pressure with normal cerebrospinal fluid (CSF) composition and negative cerebral imaging studies (i.e. computed tomography or magnetic resonance imaging scanning). It is usually accompanied by papilledema, but this is not a requirement for the diagnosis of PTC451. In this situation, sustained elevations in CSF pressure should be documented through successive lumbar punctures or by prolonged intracranial pressure monitoring, if necessary452. Sometimes, the symptoms of PTC resolve with the initial “diagnostic” lumbar puncture. If this occurs, no further medical treatment is required. If symptoms persist, temporary discontinuation or dose reduction of ATRA, analgesics, and administration of steroids and acetazolamide are the mainstays of the medical treatment of PTC. Acetazolamide is administered in initial doses of 25 mg/kg/day and the dose titrated upward until clinical response is attained (maximum dose 100 mg/kg/day). Electrolytes must be monitored to evaluate for the development of hypokalemia and acidosis. If acetazolamide is ineffective then prednisone can be given at a dose of 2 mg/kg/day for 2 weeks followed by a 2-week taper453.
6.17.3 Pregnant women
Although not well known, the incidence of APL during pregnancy is low. Management of this challenging situation is mainly conditioned by the gestational age and the attitude of the patient to risk, both for herself and the fetus. Decision making requires the participation of all specialized physicians implied in the leukemia treatment and the management of gestation and future newborn.
Treatment at the first trimester
Given the teratogenic potential of chemotherapy454, ATRA455 and arsenic trioxide456 on the fetus, therapeutic options for patients diagnosed during the first trimester are extremely limited in terms of the chance of successful outcome for the fetus. The crucial decision in this situation is whether to continue with the pregnancy or not. If elective abortion is unacceptable, administration of chemotherapy alone is recommended on a type R basis. Because a larger experience, daunorubicin is preferred to idarubicin454,457. ATRA must no be administered during the first trimester and ATO is contraindicated during all pregnancy. If remission is achieved with chemotherapy and the pregnancy is progressing normally, treatment with ATRA could be administered later during the second and third trimesters.
Female patients with APL treated conventionally should be routinely advised against conceiving while exposed to ATRA or ATO for consolidation and maintenance therapy.
Treatment at second and third trimester
Although limited information is available, at this time of pregnancy it seems reasonable to base the treatment in the use of ATRA and/or anthracycline-based chemotherapy. Although it has been suggested that chemotherapy does not cause congenital malformation, it increases the risk of abortion, prematurity, low birth weight, neonatal neutropenia, and sepsis as recently reviewed by Culligan and colleagues454. Stringent fetal monitoring, with particular emphasis on cardiac function, is recommended for patients receiving ATRA alone or combined with chemotherapy during pregnancy458,459. Taken into account this aspects, two different treatment schedules could be used on and individual basis: 1. Sequential treatment with ATRA followed by ATRA and chemotherapy after delivery; 2. Treatment with simultaneously administration of ATRA and chemotherapy, which is the standard approach for no pregnant patients. The former allows achieve good CR rate, although relapse risk is expected to be higher389. Chemotherapy should not be delayed after delivery and good MDR monitoring is strongly recommended for early detection of relapse or resistance.
Following successful delivery, breast feeding is contraindicated if chemotherapy or ATO is needed. The rest of management does not differ from other patients with APL.
6.17.4 Therapy-related APL
Current data would suggest that patients with tAPL have a relatively favorable prognosis; although the results of one study indicated a higher incidence of early death during treatment353. At present there is generally no reason to manage these patients in a different manner to those with de novo APL. However, in a significant number of patients with tAPL, the use of conventional anthracycline-based regimens is limited by previous anthracycline exposure and/or cardiac impairment induced by treatment of the primary condition. In such situations, ATO in combination with ATRA provides an option for consolidation following standard induction therapy or as first-line treatment using schedules such as those published by the MD Anderson group414.
6.17.5. Genetic variants of APL
Because the nature of the RARA-fusion partner can be critical to determine the response to ATRA and ATO460, it is reasonable that, as a general rule, patients with ATRA-sensitive variants should be treated with standard protocols involving ATRA combined with anthracycline-based chemotherapy, while those with ATRA-resistant variants should be managed with AML-like approaches. In this regard, NuMA-RARA, NPM1-RARA and FIP1L1-PDGFRA are known to be ATRA sensitive, while others are resistant (STAT5b-RARA)370, relatively resistant (PLZF-RARA), or their sensitivity to ATRA is unknown (PRKAR1A-RARA)371. Sensitivity to ATO has not been documented outside PML-RARA positive APL, except for PLZF-RARA positive APL that has been shown to be resistant461.
7. LATE SEQUELAE
7.1 Long-term sequelae
Long AML survivors are exposed to late sequelae derived from chemotherapy treatment and stem cell transplantation. One of the most significant late complications of AML treatment is anthracycline related cardiotoxicity. It is well known that treatment with either daunorrubicin or idarrubicin results in an increased risk of cardiotoxicity which can vary from subclinical toxicity to heart failure requiring heart transplantation as the only curative option462. The risk of cardiotoxicity increases with cumulative doses of antrhacyclines and it seems to be lower with the use of idarrubicin rather than daunorrubicin462,463. Anthracycline-iron complexes could be related with the generation of free radicals resulting in heart damage because heart tissue has a low concentration of antioxidant enzymes464. These free radicals can cause lipid peroxidation with the corresponding damage to the cardiac myocytes membrane465. The serum or plasma level of cardiac troponin-T466,467, carnitine468, atrial natriuretic peptide469,470 and cardiac troponin I469 has been suggested as earlier markers of anthracycline related cardiotoxicity.
Infertility is a frequent complication due to germ cells destruction. Sperm storage, oocyte and ovarian cortex cryopreservation are adviced in young patients. Other late sequelae include pulmonary fibrosis, premature arteriosclerosis, hypothyroidism, growth failure, delayed or absent puberty, cataracts, avascular necrosis, osteoporosis and functional hyposplenism.
Finally, secondary neoplasms are related to chemotherapy treatment although its frequency is low in AML patients. The risk is increased in patients undergoing allogeneic HSCT who can develop lympfoproliferative disorders, mainly related to Epstein-Barr virus, myelodisplastic syndromes or solid tumors471.
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Dr. Renato Bassan (Associate Editor)
Ospedali Riuniti – Bergamo, Italy
Dr. Gemma Gatta (Consultant)
Istituto Nazionale Tumori – Milan, Italy
Dr.Federico Moscardó (Author)
University Hospital La Fe – Valencia, Spain
Dr. Carlo Tondini (Editor)
START Clinical Editor – Ospedali Riuniti – Bergamo, Italy
Prof. Gert J. Ossenkoppele (Reviewer)
VU University Medical Center – Amsterdam, The Netherlands
Dr. Miguel A. Sanz (Author)
University Hospital La Fe – Valencia, Spain
Dr. Jorge Sierra (Author)
Hospital de la Santa Creu i Sant Pau – Barcelona, Spain