Clinical, Biological Profile and Outcome of Biphenotypic Acute Leukemia: a Case Series.

Abstract 1683 Biphenotypic acute leukemia (BAL) is a very rare type of acute leukemia, which presents a high heterogeneity and poor prognosis. We identified 51 cases (3.0%) BAL from 1693 newly diagnosed acute leukemia patients according to the EGIL scoring system between January 2003 and July 2009. The biological features, treatment and outcome of 39 evaluable BAL patients were analyzed retrospectively. There were 23 (59.0%) cases of myeloid and B-lymphoid (M/B) phenotype, 14 (35.9%) cases of myeloid and T-lymphoid (M/T) phenotype, one case (2.6%) of trilineage phenotype or B-lymphoid and T-lymphoid phenotype respectively. The high expressions of CD34 (84.6%) and HLA-DR (54.5%) on the blast cells of BAL support the notion that BAL probably arises from hemopoietic stem/progenitor cells. It seemed that CD7-positive patients had poorer median survivals comparing with those CD7-negative patients, however, there was no statistical difference ( P =0.076). Abnormal karyotypes were detected in 75.7% of 37 BAL patients with valid analysis and displayed a high heterogeneity, which were associated with structural rearrangement and numerical abnormalities including t(8;21) (16.2%), t(9;22) (13.5%), structural rearrangement of 11 chromosome (16.2%), 11q23 (5.4%), complex karyotype (21.6%) and other abnormal karyotypes (10.8%). Combined regimens for both AML and ALL, ALL-type regimens appeared a better complete remission (CR) rate than AML-type regimens (71.4% vs. 63.6% vs. 33.3%). The median survival for overall survival (OS) and disease-free survival (DFS) in our series was 14 and 12 months, the probability of OS and DFS at 2 years was 26.0% and 18.5%, respectively. No statistical differences were observed in CR rate, OS and DFS between M/B and M/T cases. It showed that BAL patients with complex karyotype or rearrangement of 11 chromosome had a significantly worse survival in contrast to normal karyotype, t(8;21) and t(9;22) group ( P= 0.001). Although BAL with t(8;21) seemed to be appeared a better survival than normal karyotype and t(9;22) group, there were no statistical significance ( P= 0.436). Our data indicate that combined-type regimens or ALL-based protocols are more effective and complex karyotype, rearrangement of 11 chromosome have the unfavorable prognosis for BAL. Disclosures: No relevant conflicts of interest to declare.