Prognostic Implications of the Immunophenotype in Biphenotypic Acute Leukemia.

Biphenotypic acute leukemia (BAL) is a rare yet defined type of acute leukemia. We investigated the incidence, clinicopathologic characteristics, and clinical outcomes of BAL in Korean adults. The present study retrospectively analyzed clinicopathological and clinical data from 43 adult patients with BAL, defined using the EGIL scoring system, from 11 Korean institutes. The incidence of BAL was 2.1% among acute leukemias; 2.3% in male and 1.9% in female. Median age of 43 BAL patients, 25 males and 18 females, was 38 years (range, 16–74). The immunophenotype was myeloid/B-lymphoid (M+B) in 31 (72.1%), myeloid/T-lymphoid (M+T) in 10 (23.3%), and B/T-lymphoid (B+T) and myeloid/B/T-lymphoid (M+B+T) in one (2.3%) each. 37 patients had the results of cytogenetic analyses and Ph chromosome (n=14, 37.8%) was the single most common abnormal finding. Intensive induction chemotherapy was given in 36 of 43 patients: AML-type in 13 (36.1%), ALL-type in 8 (22.2%), and combined type in 15 (41.7%). Complete remission (CR) was induced in 29 patients (80.6%). The CR rate was significantly lower in M+T (5 of 9, 55.6%) than M+B (22 of 25, 88.0%) (P=0.039). Other unfavorable factors for CR were absence of CD19 (P=0.029) or CD20 (P=0.046), and presence of CD2 (P=0.040). The CR rates were not significantly different according to cytogenetic finding or type of induction chemotherapy. After median follow-up duration of 712 days among surviving patients, 11 patients relapsed with median relapse-free survival (RFS) of 3.08 years and 4-y RFS of 38.3% and 18 patients died with median overall survival (OS) of 2.49 years and 4-y OS of 30.1%. Multivariate analysis showed that high leukocyte counts (≥ 30,000/μl) at diagnosis (OR, 5.922; 95% CI, 1.379–25.429; P=0.017) was an independent unfavorable prognostic factor for RFS, and high leukocyte counts at diagnosis (OR, 9.348; 95% CI, 3.014–28.993; P<0.001) and M+T phenotype (OR, 3.259; 95% CI, 1.136–9.344; P=0.028) were independent unfavorable prognostic factors for OS. In summary, BAL was found in 2.1% of adult acute leukemias and M+T phenotype showed significantly poorer response to induction chemotherapy and inferior overall survival compared to M+B phenotype.