Acute megakaryocytic leukemia: the Eastern Cooperative Oncology Group experience

Acute megakaryocytic leukemia (AMegL) is a rare subtype of acute myeloid le ukemia (AML) evolving from primitive megakaryoblasts. Because of its rarity and the lack of precise diagnostic criteria in the past, few series of adu lts treated with contemporary therapy have been reported. Twenty among 1649 (1.2%) patients with newly diagnosed AML entered on Eastern Cooperative On cology Group (ECOG) trials between 1984 and 1997 were found to have AMegL. The median age was 42.5 years (range 18-70). Marrow fibrosis, usually exten sive, was present in the bone marrow. Of the 8 patients who had cytogenetic studies performed, abnormalities of chromosome 3 were the most frequent. T he most consistent immunophenotypic finding was absence of myeloperoxidase in blast cells from 5 patients. In the most typical 3 cases, the leukemic c ells were positive for one to 2 platelet-specific antigens in addition to l acking myeloperoxidase or an antigen consistent with a lymphoid leukemia. M yeloid antigens other than myeloperoxidase and selected T-cell antigens (CD 7 and/or CD2) were frequently expressed. Induction therapy included an anth racycline and cytarabine in all cases. Complete remission (CR) was achieved in 10 of 20 patients (50%). Two patients remain alive, one in CR at 160+ m onths. Resistant disease was the cause of induction failure in all but 3 pa tients. The median CR duration was 10.6 months (range 1-160+ months). The m edian survival for all patients was 10.4 months (range 1-160+ months). Alth ough half of the patients achieved CR, the longterm outcome is extremely po or, primarily attributable to resistant disease. New therapeutic strategies are needed. (Blood. 2000;96:2405-2411). (C) 2000 by The American Society o f Hematology.