A. Characteristics

1. Increased number of (pre-)myeloid cells with arrested maturation
   1. Clonal disorder of early myeloid, erythroid or megakaryocytic "blasts"
   2. Represents a differentiation arrest at early stage
2. Epidemiology
   1. Most common malignant myeloid disorder in adults
   2. Incidence is ~2.6 per 100,000 persons per year in USA
   3. About 10,000 new cases per year in USA
   4. Peak age group is >65: annual incidence is ~14 per 100,000 persons
   5. Over 75% of AML patients are >60 years old
   6. Overall survival >5 years is ~40% for patients <65 years
3. Frequently have chromosomal translocations
4. Most subtypes contain granules histologically (compare with lymphocytic leukemias)

B. Etiology / Associations

1. Radiation Exposure
2. Chemicals and Drugs [5]
   1. Benzene
   2. Alkylating agents: cyclosphosphamide, chlorambucil, melphalan, others (~20X increase)
   3. Topoisomerase II Inhibitors such as etoposide, anthracyclines, mitoxantrone [4]
   4. Platinum chemotherapies (~5X increased risk)
3. Chronic Marrow Disease
   1. Myelodysplastic syndromes (MDS) - conversion to acute leukemia; poor prognosis
   2. Myeloproliferative disease - CML transformation to blast crisis
   3. Congenital chromosomal anomalies including trisomy 21 (Down Syndrome) [20]
4. Chloroma
   1. Extramedullary tumor of granulocytic lineage
   2. Strong association with acute myeloid leukemia and myelodysplastic syndromes
   3. Early anti-leukemic therapy may prevent progression to AML
5. Increased risk in cockpit crew members flying >5000 hours (5.1X increase) [19]
6. Down Syndrome [25]
   1. Increased incidence of leukemia, mainly acute myeloid form [20]
   2. Transient myeloproliferative disorder associated with trisomy 21 also occurs [25]

C. AML Subtypes and Genetics (Frequency) [21]

1. M0 - undifferentiated leukemia, indeterminent type; 5% of cases
   1. inv(3q26) involving EVI1 gene
   2. t(3;3)
2. M1 - myeloblastic leukemia without differentiation; 20%
3. M2 - myeloblastic leukemia with differentiation (granules); 30%
   1. t(8;21) involving AML1-ETO (confers good prognosis)
   2. t(6;9) involving DEK-CAN
4. M3 - acute promyelocytic leukemia; 10%
   1. t(15;17) involving PML-RARa (confers good prognosis)
   2. t(11;17) involving PLZF-RARa or NPM-RARa (confer good prognosis)
5. M4 - myelomonocytic; 20% (see below)
6. M5 - monocytic; 10%
   1. 11q23 involving the MLL gene (confers poor prognosis)
   2. t(8;16) involving MOZ-CBP
7. M6 - erythroblastic (>50% erythroid type blasts); 5%
8. M7 - megakaryocytic; very rare
9. Secondary AML - post-chemotherapy, radiation, MDS
   1. Chromosomal loss: 5q-, 7q- (poor prognosis)
   2. 11q23 involving the MLL gene (confers poor prognosis)
10. Nucleophosmin Localization [7]
    1. Normally a nucleus-associated protein
    2. Abnormal cytoplasmic localization in 60% of patients with normal karyotype AML
    3. Increased frequency of Flt3 mutations in patients with cytoplasmic nucleophosmin
    4. Flt3 (a tyrosine kinase) mutations associated with constitutive kinase activity
    5. Flt3 inhibitors are in clinical development for AML

D. Cytogenics and World Health Organization (WHO) Classification [1,18,21]

1. Cytogeneic features are most important current stratification / prognostic method
   1. 40-50% of adult AML associated with normal karyotype
   2. Most cytogenetic anomalies involve translocations of DNA binding transcription factors
2. WHO Classifications
   1. With t(8;21)(q22;q22) or t(15;17)(q22;q12) or inv(16)(p13q22) - all good prognosis
   2. AML secondary to chemotherapy - poor prognosis
   3. With chr 11q23 abnormalities - poor prognosis
   4. With chr 5 or 7 anomalies, poor prognosis
   5. With multilineage dysplasia - poor prognosis
   6. With normal karyotype - variable outcomes
   7. Therapy related AML and myelodysplastic syndrome (MDS)
3. AML1: AML Translocation t(8;21) Gene
   1. About 40% of cases of M2 Subtype of AML have AML1-CBFß translocation
   2. Creates a fusion DNA binding protein
   3. AML1-CBFß codes for DNA binding subunit
   4. CBFß transcription factor (chromosome 21) regulates a number of hematopoietic genes
   5. AML1 also translocated in childhood acute lymphocytic leukemia (ALL) t(12;21)
   6. The other subunit of CBFß on chromosome 16 is involved in t(16;16) and inv(16)
   7. These chromosome 16 alterations are mainly found in M4Eo (see below)
4. Chromosome 11q13 (MLL) Structural Alterations
   1. Common (85%) in secondary AML due to topoisomerase inhibitor therapy
   2. Found in 6-8% of primary AML, usually M4 or M5
   3. 5' portion of mixed lineage leukemia (MLL) gene fuses to gene on another chromosome
   4. Chromosomes 6, 9, 10, 17, or 19 are most frequently involved
5. Chemotherapy Associated M3 AML (APL) [10]
   1. Topoisomerase II inhibitors increase risk of APL with t(15;17)
   2. Mitoxantrone induces breaks in an 8-bp region in PML intron 6 leading to translocations
   3. Short, homologous DNA sequenes within PML and RARa suggest DNA repair after topoisomerase II inhibition occurs by nonhomologous end-joining pathway
6. Mutated ras oncogenes 15-50%
7. Disruption of RB1 or WT1
8. Gene Expression and AML
   1. Gene expression profiling has shown at least two different prognostic subsets with normal karyotype in adult AML, and various AML genetic profiles with prognostic implications [14,15]
   2. microRNA signature in high-risk, cytogenically normal AML associated with clinical outcome [29]
9. Cytogenetically Normal AML [8]
   1. Most patients with cytogenically normal AML have gene mutations
   2. NPM1 (nucleophosmin) mutations: 53%
   3. FLT3 (fms-related tyrosine kinase 3): 31% internal tandem duplications, 11% in kinase-domain
   4. CEBPA (CCAAT/enhancdr binding protein alpha): 13%
   5. MLL (mixed lineage leukemia): 7%
   6. N-Ras (neuroblastoma RAS homolog): 13%
   7. Mutant NPM1 without internal tandem duplications associated with 56% reduced relapse risk
   8. Mutant CEBPA reduced relapse risk >50%
   9. Likely that gene expression profiling parallels some of these prognistic and mutational data

E. Presentation

1. Related to replacement of normal marrow with tumor cell blasts
2. Presentation similar to other marrow disorders and amongst different AML subtypes
3. Fever - neutrophils function poorly; immature blasts do not fight infections
4. Fatigue, pallor and weakness due to anemia
5. Bleeding due to thrombocytopenia
6. Bleeding due to coagulopathy (seen with APML, M3 subtype)
7. Central nervous system involvement may mimic meningitis [18]
8. Arthritis - direct infiltration of leukemic cells (usually M4 or M5) [30]

F. Diagnosis

1. Blood Smear - Auer Rods are pathognomonic
2. Bone Marrow
   1. Aspirate - cell type, with special stains
   2. Biopsy - architecture
3. Histochemistry
   1. Periodic Acid-Schiff (PAS) Stains positive for lymphocytic lineage cells
   2. PAS stains negative for myelomonocytic lineage cells
   3. Specific Esterase - Positive for myelomonocytic, negative for lymphocytic
   4. Non-Specific Esterase - positive for monocytic only
   5. Peroxidase - positive for granulocytic only
4. Surface Markers
   1. AML is CD33 and CD13 positive; ALL is negative for both
   2. CD14 is the Fc receptor found on some of the more mature ALL
   3. Lack of surface Ig, cytoplasmic Ig, or T cell receptors
5. Chromosomal Abnormalities (karyotyping; see below)
   1. Useful for definitive classification and prognosis
   2. Increased chromosomal abnormalities associated with poorer outcomes
   3. AML related to MDS has large numbers of abnormalities

G. Myelomonocytic Leukemia (M4)

1. Types
   1. Common Form - immature monocytes and granulocytes
   2. M4-Eo: M4 with eosinophilia
2. Chromosomal Abnormalities with M4 [29]
   1. 11q23 involving the MLL gene (confers poor prognosis)
   2. t(3;3)
   3. inv(3q26) invovling EVI1
   4. t(6;9) involving DEK-CAN
3. Chromosomal Abnormalities with M4Eo [1,29]
   1. M4Eo - inv(16)(p13q22) pericentric inversion
   2. This inversion places a transcription factor (CBFß) and muscle myosin H chain (MYH11)
   3. t(16;16) also found

G. Treatment [1,2,23]

1. Treatment Overview [1,6]
   1. All patients receive induction therapy with chemotherapy
   2. Two phases: induction (of remission) and consolidation (mainenance) of remission
   3. About 75% of patients will have a complete remission (CR) with 1-2 cycles of induction
   4. Median duration of first CR is 15 months
   5. These patients are offerred consolidation therapy or bone marrow transplant (BMT)
   6. Median duration of second CR is 4-8 months
   7. Overall 5 year survival rates are in the ~60% range for patients age <60 years
   8. Poor response to induction: certain chromosomal abnormalities, secondary AML, leukocyte count >20K/µL, unfavorable immunophenotype, age >60 years, mdr1 protein
   9. Gene expression profiling of AML may identify good and poor responders [14,15]
2. Induction therapy (Good Performance, Age <60 years)
   1. Cytosine Arabinoside (AraC) x 7 days with daunorubicin or idarubicin x 3 days
   2. Addition of other drugs do not appear to improve CR rates
   3. High Dose AraC (HiDaC) may also be used for induction
   4. Evaluate bone marrow for leukemic cells at day 14
   5. Reinduction therapy if leukemic cells seen on day 14
   6. CR after 1-2 cycles of induction therapy (~75% of patients) is a good prognostic sign
   7. A third cycle (usually 5 days AraC and 2 days idarubicin) may then be given
   8. Other drugs are used in patients (~25%) who do not achieve a CR (below)
   9. Hematopoietic stimulating factors are used to improve bone marrow recovery (below)
3. Induction in Elderly (>60 years) Patients [1]
   1. Standard drugs (3+7) but at reduced doses for 3-6 cycles
   2. Investigational Agents (such as clofarabine, Clolar®)
   3. Paliative Care
   4. Median survival time for elderly AML is 10 months with standard therapy
   5. Standard doses of induction drugs lead to ~15% treatment related mortality
4. Complete Remission (CR) Definition
   1. Bone marrow with <5% blasts
   2. Neutrophil count >1000/µL
   3. Platelet count >100,000/µL
   4. CR without platelet recovery is called "CRp"
5. Therapy Following Complete Remission after Induction
   1. Consolidation with HiDaC - doses are ~30X higher than induction
   2. HiDaC associated with extreme myelosuppression and neurotoxicity (not cardiotoxic)
   3. BMT may also be offerred, but benefits are questionable (see below) [20]
6. Failed Complete Remission Induction
   1. Mitoxantrone
   2. High dose cyclophosphamide
   3. Investigational agents such as clofarabine
   4. Poor prognostic sign
7. Bone Marrow Transplantation (BMT) [6]
   1. Allogeneic transplant preferred if match can be found (<25% of patients)
   2. Autologous transplant with or without marrow purging can also be used
   3. Autologous marrow is purged with 4-hydroxycyclophosphamide (perfosfamide)
   4. BMT should generally be used only in patients with complete responses
   5. Overall, similar results with autologous BMT versus intensive chemotherapy in adults [5]
   6. In children with acute leukemia, umbilical blood cell transplant with up to 2 HLA mismatches has similar 5 year outcomes to allogeneic transplant with less GVHD [28]
   7. BMT groups had higher complications and hospital stays
   8. Patients who relapsed and got high dose chemotherapy can then get BMT
   9. Autologous BMT added to intensive chemotherapy leads to higher 7 year or equal 4 year disease free survival compared to intensive chemotherapy alone [9,22]
   10. Survival benefit in the MRC study [9] was only present in patients living >2 years
   11. High dose chemotherapy and autologous BMT in children had similar good results
   12. Increasing dose of infused, T-cell depeleted donor cells increases engraftment [11]
   13. T cell depleted stem cells will engraft without GVHD even with HLA mismatch [11]
   14. Mismatches at HLA-A and HLA-C, but not HLA-D associated with GVHD [12]
   15. Improved initial chemotherapy is as effective, and perhaps safer, than early allo- or autologous BMT except for first complete remission with bad prognostic karytype [6]
   16. Therefore, BMT should probably be reserved for second line, particularly with good karyotypic prognosis [6]
   17. BMT with anergic (CD28 blocked) histoincompatible bone marrow is experimental [13]
8. Gemtuzumab (Mylotarg®) [22]
   1. Recombinant human monoclonal antibody (Ab) to CD33 linked to calicheamcin toxin
   2. CD33 expressed on leukemic blasts in >80% of patients
   3. Calicheamicin is released in lysosomes of target cell and binds to DNA minor groove
   4. FDA approved for treatment of CD33+ AML in first relapse instead of chemotherapy
   5. Usually give two doses, 14 days apart
   6. Complete remission occurs in ~30% of patients given gemtuzumab
   7. Some acute cytokine release symptoms occur within 4 hours of dosing
   8. Nearly all patients develop severe neutropenia and thrombocytopenia
9. Hormonal Therapy
   1. Retinoic acid induced differentiation of M3 leukemia
   2. Colony stimulating factors - may induce differentiation of certain leukemias
10. Colony Stimulating Factors (CSF) [1]
    1. All chemotherapy protocols are followed by a period of bone marrow aplasia
    2. G-CSF (filgrastim) and GM-CSF do not stimulate growth of leukemic cells
    3. Both GM-CSF and G-CSF were studied in elderly (>60-65 years old) patients receiving chemotherapy for AML
    4. No improvement in mortality with G- or GM-CSF at two months to five years
    5. Slight reduction in neutropenia but no reduction in infection episodes
    6. Pre-chemotherapy priming with G(M)-CSF has been used to induce leukemic cells into cycling making them more susceptible to chemotherapy
    7. Pre-chemotherapy G-CSF improved disease free survival but not overall survival, but did improve overall survival in standard-risk AML [3]
    8. Erythropoietin given for anemia
    9. Lymphocyte depleted platelets given for counts <10K/µL [16,17]
    10. Thrombopoietin (TPO), IL-11, other platelet stimulants are also available
11. Clofarabine (Clolar®) has shown very good single agent activity in adult high risk AML

H. Complications

1. Infection
   1. Most common cause of death in AML
   2. Prophylaxis with oral antibiotics and antifungal agents during initial chemotherapy
   3. Posaconazole superior to fluconazole and itraconazole for prophylaxis of fungal infections and overall mortality in AML or myelodysplastic syndrome receiving chemotherapy [26,27]
   4. Institute broad spectrum antibiotics (such as mezlocillin + gentamicin) for all fevers
   5. Persistent fever on Antibiotics: add acyclovir and/or anti-fungals
   6. Most infections thought to be from enteric gram negative rods
   7. Perirectal lesions and catheter infections also fairly common (Gram positive cocci)
2. Tumor Lysis Syndrome
   1. Most common with rapidly growing leukemias
   2. Occurs with tumor lysis during chemotherapy
   3. High risk in patients with baseline renal insufficiency
3. Extramedullary Spread of Leukemia
   1. M4 and M5 types most common
   2. Invasion of skin, visceral organs, meninges
   3. Abnormal macrophages thought to be major offender
4. Leukostasis
   1. High tumor cell numbers and large cell size block cappilaries
   2. Capillary sludging is particularly problematic in the brain and lungs
   3. Therefore, strokes and/or respiratory failure can occur
   4. Renal, myocardial and other infarctions can occur
5. DIC - more common with M3
6. Late leukemias - probably related to alkylating agent chemotherapies

I. Prognosis [1]

1. Overall [6,9]
   1. Children generally do better than adults
   2. With chemotherapy alone, 7 year survival is 45%
   3. With BMT, 7 year survival is 57%
   4. "Good" risk patients do better than poor risk
   5. Good risk factors include M3 morphology, karyotype (t8:21, t15:17, inv16)
   6. Poor risk includes residual blast-cell in bone marrow after course 1 >20%
   7. Poor risk also includes abnormalities of chromosome 5 or 7, or complex karyotype
2. Predictors of Poor Response to Chemotherapy
   1. Unfavorable karyotype
   2. Age >60 years
   3. Secondary AML (especially to MDS or chemotherapies)
   4. Poor performance score
   5. Features of multidrug resistance
   6. White cell count >20K/µL
   7. Unfavorable immunophenotype
   8. CD34 positivity is a relatively week prognostic marker
3. Predict Relapse
   1. Unfavorable karyotype (multiple and specific abnormalities)
   2. Age >60 years
   3. Delayed response to induction chemotherapy
   4. Features of multidrug resistance
   5. White cell count >20K/µL
   6. Female sex
   7. Elevated lactate dehydrogenase (LDH) level
   8. Autonomous growth of leukemic cells
   9. Residual disease burden (see below)
4. Unfavorable Karyotype (15% of cases)
   1. More than two abnormalities
   2. Monosomies of chromosomes 5 or 7
   3. Deletion of chrom 5q
   4. Abnormalities of chrom 3q
5. Favorable Karyotype
   1. APML: t(15;17)
   2. t(8;21)
   3. inv(16)
6. Multidrug Resistance Genes
   1. Overexpression of these genes associated with resistance to multiple agents
   2. MDR1 (multidrug resistance protein 1)
   3. MRP (MDR1 related protein)
   4. LRP (lung resistance protein)
7. Residual Disease [24]
   1. Cures are possible in AML
   2. Presence of residual disease reduces chances for cure
   3. Histopathological absence of blast cells does not accurately predict cures
   4. Minimal residual disease (MRD) can be quantitated using highly sensitive DNA probes
   5. Polymerase chain reaction (PCR) specific for blast cell DNA changes developed
   6. PCR can detect one leukemic blast in 10,000 - 1 million cells
   7. Cures are likely possible after consolidation therapy with specific MRD levels

References

1. Estey E and Dohner H. 2006. Lancet. 368(9550):1894
2. Lowenberg B, Downing JR, Burnett A. 1999. NEJM. 341(14):1051
3. Lowenberg B, van Putten W, Theobald M, et al. 2003. NEJM. 349(8):743
4. Mistry AR, Felix CA, Whitmarsh RJ, et al. 2005. NEJM. 352(15):1529
5. Travis LB, Holowaty EJ, Bergfeldt K, et al. 1999. NEJM. 340(5):351
6. Burnett AK. 1998. NEJM. 339(23):1699
7. Falini B, Mecucci C, Tiacci E, et al. 2005. NEJM. 352(3):254
8. Schlenk RF, Dohner K, Krauter J, et al. 2008. NEJM. 358(18):1909
9. Burnett AK, Goldstone AH, Stevns RMF, et al. 1998. Lancet. 351(9104):700
10. Mistry AR, Felix CA, Whitmarsh RJ, et al. 2005. NEJM. 352(15):1529
11. Aversa F, Tabiliio A, Velardi A, et al. 1998. NEJM. 339(17):1186
12. Sasazuki T, Juji T, Morishima Y, et al. 1998. NEJM. 339(17):1177
13. Guinan EC, Boussiotis VA, Neuberg D, et al. 1999. NEJM. 340922):1704
14. Bullinger L, Dohner K, Bair E, et al. 2004. NEJM. 350(16):1605
15. Valk PJM, Verhaak RGW, Beijen MA, et al. 2004. NEJM. 350(16):1617
16. Rebulla P, Finazzi G, Marangoni F, et al. 1997. NEJM. 337(26):1870
17. Trial to Reduce Alloimmunization to Platelets Study Group. 1997. NEJM. 337(26):1861
18. Ballen KK and Hasserjian RP. 2005. NEJM. 352(3):274 (Case Record)
19. Gundestrup M and Storm HH. 1999. Lancet. 354(9195):2029
20. Hasle H, Clemmensen IH, Mikkelsen M. 2000. Lancet. 355(9199):165
21. Stewart AK and Schuh AC. 2000. Lancet. 355(9213):1447
22. Gemtuzumab. 2000. Med Let. 42(1083):67
23. Drugs of Choice for Cancer Chemotherapy. 2000. Med Let. 42(1087):83
24. Yin JL and Grimwade D. 2002. Lancet. 360(9327):160
25. Wolfe LC, Weinstein HJ, Ferry JA. 2003. NEJM. 348(25):2557 (Case Record)
26. Posaconazole. 2006. Med Let. 48(1248):93
27. Cornely OA, Maertens J, Winston DJ, et al. 2007. NEJM. 356(4):348
28. Eapen M, Rubinstein P, Zhang M, et al. 2007. Lancet. 369(9577):1947
29. Marcucci G, Radmacher MD, Maharry K, et al. 2008. NEJM. 358(18):1919
30. Schwarzberg AB, Alexander CB, DeAngelo DJ, Helfgott SM. 2008. NEJM. 358(23):2496 (Case Discussion)