[1393] Mixed Phenotype Acute Leukemia (MPAL): A Study of 61 Cases Using WHO and EGIL Criteria.

Olga K Weinberg, Mahesh Seetharam, Li Ren, Ash Alizadeh, Daniel A Arber. Stanford University, CA

Background: The 2008 WHO classification system grouped bilineal and biphenotypic acute leukemias together under a new heading of MPAL. The lineage specific marker criteria have also changed for a diagnosis of MPAL. The goal of this study is to characterize the clinical significance of this new group.
Design: Sixty-one patients were diagnosed as MPAL at Stanford University from 1995 to 2009 using either European Group for the Immunologic Classification of Leukemia (EGIL) criteria or 2008 WHO criteria were studied. Overall survival (OS) and progression free survival (PFS) were retrospectively determined and compared using Kaplan-Meier and multivariate Cox proportional hazards regression. Clinical outcome of MPAL patients was compared with 177 acute myeloid leukemia (AML) patients and 387 acute lymphoblastic leukemia (ALL) patients also diagnosed at Stanford.
Results: The 61 patients included 36 males and 25 females with a median age of 32 years and included 23 patients 21 years of age or younger. Twenty patients diagnosed as acute biphenotypic leukemia using EGIL criteria did not fulfill 2008 WHO criteria for MPAL. Only two patients diagnosed as MPAL did not meet criteria for acute biphenotypic leukemia using EGIL criteria. Ten patients had two separate blast populations and would be considered as acute bilineal leukemia under the EGIL. Cytogenetic data were available in 42 patients and the most common abnormality was t(9;22); though present in only 4 patients. Clinical outcome data showed no significant differences between MPAL patients using new WHO criteria and those using EGIL criteria (OS p=0.639, PFS p=0.474). Even after dividing patients into childhood and adult groups, no difference in outcome between MPAL patients using new WHO criteria and those using EGIL criteria was identified. However, patients <21 years of age had better OS as compared to patients over 21 both in the EGIL group and in the WHO group (EGIL p=0.0403, WHO p=0.0601). Comparison of outcome by expression of MPO, cytoplasmic CD3, CD19, CD79a, CD10 showed no significant difference in OS or PFS. As compared with all 177 AML patients, all MPAL patients had better OS (p=0.0003) and PFS (p=0.0001). However, no difference in OS between MPAL and ALL patients was present (p=0.599).
Conclusions: As defined by the 2008 WHO classification, fewer patients are now classified as MPAL than using EGIL criteria. EGIL criteria, however, may be more predictive of prognosis in children than those of the 2008 WHO. In our study, MPAL patients have similar overall survival to ALL patients and have better OS and PFS than AML patients.
Category: Hematopathology

Monday, February 28, 2011 1:00 PM

Poster Session II # 190, Monday Afternoon

 

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