Characteristics and Prognosis of Patients (pts) with Acute Megakaryocytic Leukemia (AMegL) Treated at M.D. Anderson Cancer Center Since 1987.

AMegL is a rare form of acute myeloid leukemia (AML) associated with poor prognostic features. Here, we report the experience at M.D. Anderson Cancer Center from 1987 to 2003. Among 1861 pts with newly diagnosed AML (excluding APL), 38 pts (2%) had AMegL. The diagnosis of AMegL was based on (i) morphological features defined by FAB classification and (ii) immunophenotypypical positivity for CD42 and CD61 whenever available. All 38 pts received induction chemotherapy containing cytarabine and anthracyclines. Sixteen (42%) were males; median age was 54 years (range 21–78); 11 (29%) had antecedent hematologic disorder (AHD) and/or MDS, and 4 (11%) had previously received chemotherapy for other malignancies. Median white blood cell count at diagnosis was 3.5x10⁹/L (0.5–49.9), hemoglobin 7.8 g/dl (3.2–10.9), platelet count 34.5x10⁹/L (5–2292), and the median bone marrow blast percentage was 30% (0–80). For pts with <30% bone marrow blasts, diagnosis of AMegL was supported by peripheral blood blasts ≥30%. Significant bone marrow fibrosis was found in 24 pts (63%). Cytogenetic analysis was available in 30 pts (79%) due to insufficient material or insufficient metaphases. Twenty-seven pts (71%) showed abnormalities: deletion 7 in 15 pts (39%), deletion 5 in 14 (37%), chromosome 3 abnormality in 6 (16%) and trisomy 8 in 4 (11%). Philadelphia chromosome was detected in 2 pts (5%). Sixteen pts (42%) achieved a complete remission (CR). None of 22 pts with primary refractory disease achieved a complete remission from subsequent chemotherapies. Median overall survival of all AMegL pts (n=38) was 24 compared to 38 weeks for the control group (non AmegL AML pts, excluding APL,N=1823) (p<0.01). Median disease free survival of pts with AMegL (n=16) and other AML (n=1031) was 23 and 52 weeks, respectively (p<0.001). Two pts with primary refractory disease and three who developed relapsed disease eventually underwent allogeneic stem cell transplantation. Median survival after stem cell transplantation was 21 weeks. In summary, AMegL is a rare form of AML, which is observed in pts with AHD and/or MDS or as secondary leukemia. AMegL is highly associated with poor cytogenetic abnormalities, translating into a low CR rate and dismal outcome.