Clinical Management of Leukemia

1. Clinical Management of Leukemia Maria R. Baer, M.D. University of Maryland Greenebaum Cancer Center November 7, 2008

2. Clonal bone marrow disorders Acute leukemias Acute myeloid leukemia (AML) Acute lymphoblastic leukemia (ALL) Chronic leukemias Chronic myelogenous leukemia (CML) Chronic lymphocytic leukemia (CLL) Myeloproliferative disorders Polycythemia vera Essential thrombocythemia Myelofibrosis Myelodysplastic syndromes Aplastic anemia PNH

3. Bone marrow cellularity

4. Chronic vs. Acute Myeloid Leukemia

5. Hematologic Malignancies Bone marrow cells are accessible for study with various laboratory techniques Cells can be sampled serially over time Hematologic malignancies therefore serve as models for study of other cancers

6. Hematologic Malignancies Laboratory studies have allowed understanding of biology Understanding of biology is leading to the development of new, targeted treatments with greater specificity and greater efficacy.

7. Clinical management of two leukemias AML CML

8. AML AML is biologically, cytogenetically and molecularly diverse This diversity is used in assigning prognosis, stratifying therapy and, increasingly, targeting therapy.

9. CML CML is biologically and cytogenetically uniform. Because of this uniformity, CML is the model for targeted therapy in oncology. Current efforts focus on identifying and overcoming mechanisms of resistance to targeted therapy.

10. Characterizing leukemia cells Morphology Cytochemical staining Immunophenotyping Cytogenetics Molecular diagnostics Quantification of molecular markers

11. Acute Myeloid Leukemia Morphology

12. AML Immunophenotype by Four-Color Flow CytometryCD7/CD13/CD2/CD19 302890, Fitzer, Ernest; BM; 3/24/2005 CD2+, AML inv(16) 302890, Fitzer, Ernest; BM; 3/24/2005 CD2+, AML inv(16)

13. AML Cytogenetics: t(8;21)

14. AML Cytogenetics: Complex

15. 

16. FLT3 Mutations in AML

17. This schema shows the predicted secondary structure of Pgp, MRP-1 and BCRP. Pgp has two hydrophobic transmembrane domains and two ATP binding sites. The transmembrane regions bind hydrophobic drug substrates which are likely presented directly from the lipid bilayer. Two hydrolysis events are required to transport one drug molecule. Binding of substrates to transmembrane regions stimulates the ATPase activity of Pgp, causing a conformational change that releases substrates to either the outer leaflet of membrane (from which substrates can diffuse to the medium) or extracellular space. Hydrolysis of second ATP is required to “reset” the transporter so that it can bind substrate again, completing one catalytic cycle. MRP-1 also has 2 ATP binding sites but contain five extra transmembrane regions at the N terminal. Pgp and MRP-1 share less than 20% amino acid identity. BCRP is a half transporter containing only one hydrophobic transmembrane domain and one ATP binding site. Hence BCRP requires dimerization for its function. This schema shows the predicted secondary structure of Pgp, MRP-1 and BCRP. Pgp has two hydrophobic transmembrane domains and two ATP binding sites. The transmembrane regions bind hydrophobic drug substrates which are likely presented directly from the lipid bilayer. Two hydrolysis events are required to transport one drug molecule. Binding of substrates to transmembrane regions stimulates the ATPase activity of Pgp, causing a conformational change that releases substrates to either the outer leaflet of membrane (from which substrates can diffuse to the medium) or extracellular space. Hydrolysis of second ATP is required to “reset” the transporter so that it can bind substrate again, completing one catalytic cycle. MRP-1 also has 2 ATP binding sites but contain five extra transmembrane regions at the N terminal. Pgp and MRP-1 share less than 20% amino acid identity. BCRP is a half transporter containing only one hydrophobic transmembrane domain and one ATP binding site. Hence BCRP requires dimerization for its function.

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19. Multivariable analyses for complete remission (CR) and for overall survival (OS) in cytogenetically normal AML in patients <60 years 

20. Outcome Predictors in AML Clinical Patient age de novo vs. secondary AML Laboratory Cytogenetics FLT3 mutations, NPM1, CEPBA, BAALC, ERG CD34 phenotype Mechanisms of resistance/treatment failure Multidrug resistance Pgp, MRP-1, BCRP Aberrant signal transduction FLT3, PI3k, mTOR, STAT3, VEGF

21. AML Treatment Principles Treatment Goals Induce remission Delay/prevent relapse Eradicate minimal residual disease Cure Treatment Phases Remission induction Post-remission treatment Consolidation Intensification: high-dose chemotherapy, allogeneic or autologous transplantation (Maintenance)

22. Standard “7&3” Remission Induction Therapy (1973) Cytarabine 100 mg/m2/day by continuous infusion Daunorubicin 30-60 mg/m2 qd x 3 days ~ 70% remission rate Most patients relapse despite post-remission therapy

23. AML Incidence Increases with Age

24. Estimates of overall survival of newly diagnosed AML treated on ECOG protocols 1973-1997

25. DFS for Patients <60 Years (A) and >60 Years (B) According to Cytarabine Dose

26. Older AML Patients with Favorable and Intermediate Karyotypes Have Short Survival

27. Poor-Risk Features in Older AML Patients Secondary AML Antecedent myelodysplastic syndromes Therapy-related Prognostically adverse karyotypes Multidrug resistance MDR1 CD34 Hyperleukocytosis

28. AML Biology and Treatment Response in Older Adults Inferior treatment outcomes Increased frequency of factors associated with adverse prognosis in younger patients Chemoresistance even in the absence of adverse prognostic factors and in the presence of favorable prognostic factors Survival is short even for older patients who enter CR. Chemoresistance may reflect age-related changes in the hematopoietic stem cells in which acute leukemia arises.

29. Complex Karyotypes Are Associated with Low CR Rates in Older AML Patients Complex karyotypes with >3 abnormalities were associated with CR rates of 26% and 25% in MRC and CALGB series of older patients. NCCN Guidelines recommend clinical trial, low-intensity therapy or best supportive care, rather than standard cytotoxic therapy, for these patients.

31. AML Establish diagnosis by morphology and flow cytometry Initiate induction therapy or wait for prognostic data Establish prognosis using cytogenetic and molecular data Choose post-remission therapy Monitor residual disease Targeted therapies

32. Chronic Myeloid Leukemia Morphology

33. Philadelphia Chromosome; bcr/abl

34. Dual Color, Dual Fusion

35. Gleevec

36. Mechanism of Action of Gleevec

37. Response Rates to Gleevec

38. Five-Year Follow-up of Patients Receiving Gleevec for Chronic Myeloid Leukemia

39. Frequency of Major Molecular Responses

40. Progression-Free Survival by Molecular Response

41. Definitions of Resistance PRIMARY RESISTANCE Absence of hematologic response within 3 months Failure to achieve at least minor cytogenetic response at 3 months Failure to achieve major cytogenetic response after 6 months Failure to achieve a complete cytogenetic response after 12 months ACQUIRED RESISTANCE Loss of hematologic response Loss of complete cytogenetic response Increase of 30% or more in number of Ph+ marrow metaphases Acquired cytogenetic abnormalities in the Ph+ clone Increase in the BCR-ABL/control gene ratio of one log or more on serial testing

42. Bcr-Abl-Dependent Bcr-Abl gene amplification Bcr-Abl gene mutation Drug efflux Drug inactivation Bcr-Abl-Independent Activation of downstream signaling pathway: ras, mTOR Activation of bcr-abl-unrelated leukemogenic pathways

43. BCR-ABL Mutations Detected in up 90% of patients who develop secondary resistance to Gleevec Rare in patients with primary resistance Caveat: PCR techniques used may only identify most dominant clones

44. BCR-ABL Mutations

45. Treatment of imatinib-resistant CML Increase dose of imatinib Second generation bcr-abl inhibitor: dasatinib, nilotinib Clinical trial

46. CML Establish diagnosis by morphology and cytogenetic and molecular data Initiate targeted therapy Monitor residual disease Look for target mutations Second-line targeted therapies

47. Conclusions Based on diversity of mutations and mechanisms causing imatinib resistance unlikely that a single agent will be effective Identification of resistance mechanisms may be able to guide therapy in future