[1504] Mixed Phenotype Acute Leukemia: Experience of a Single Institution

Chi Young Ok, Sa Wang, Pei Lin, L Jeffrey Medeiros, Jeffrey L Jorgensen. University of Massachusetts Memorial Medical Center, Worcester, MA; The University of Texas MD Anderson Cancer Center, Houston, TX

Background: Mixed phenotype acute leukemia (MPAL) is a rare form of acute leukemia. In the 1990s and 2000s, the diagnosis was established using European Group for the Immunological Characterization of Leukemias (EGIL) criteria. In 2008, the revised WHO classification modified the criteria for diagnosis of MPAL. Since 2008, there have been few publications on MPAL using the updated WHO criteria.
Design: In the past 10 years, we searched the files for all cases of acute leukemia with expression of aberrant markers (e.g. acute myeloid leukemia (AML) with lymphoid markers or acute lymphoblastic leukemia (ALL) with myeloid markers). By WHO 2008 criteria, cases that can be classified as other entities are excluded from MPAL (e.g. chronic myelogenous leukemia in blast crisis). The final study group was 41 cases of MPAL. Results from immunophenotypic, cytogenetic and molecular studies, and treatment regimens (specified in 34 patients) were reviewed. Survival differences in MPAL subgroups were also compared.
Results: The median age of all 41 MPAL patients was 47 years (range, 6-81). The male-to-female ratio was 1.3:1. The study group included 24 (59%) B/myeloid leukemias, 16 (39%) T/myeloid leukemias, and 1 (2%) B/T leukemia. Cytogenetic analysis for forty patients showed 30 (75%) cases had an abnormal karyotype, most commonly a complex karyotype (≥3 aberrations). BCR/ABL rearrangement was the most common recurrent abnormality, with t(9;22)(q34;q11.2) and/or BCR/ABL fusion genes (by FISH) seen in 6/40 (15%) cases. MLL rearrangement was found in 2/40 (5%) MPAL. The overall median survival of MPAL was 15.3 months. There was no significant difference in survival between different immunophenotypic subtypes (p= .59). Patients with BCR/ABL did not show a significant difference in survival compared to all other patients (p= .91). 22 patients were treated with ALL-directed regimens (induction with hyperfractionated cyclophosphamide, vincristine, doxorubicin and dexamethasone) and 11 patients were treated with AML-directed regimens (cytarabine and daunorubicin/idarubicin). These treatment groups did not show a significant difference in survival (p= .81).
Conclusions: MPAL represents a rare subset of acute leukemia with a poor prognosis. Most cases of MPAL harbor multiple or complex cytogenetic abnormalities. No significant differences were found in survival between different immunophenotypic subtypes or between patient groups treated with different therapeutic regimens (ALL vs. AML).
Category: Hematopathology

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 243, Monday Morning


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