Aberrant Expression of CD13 Identifies a Subgroup of Standard-Risk Adult Acute Lymphoblastic Leukemia With Inferior Survival

Abstract

The standard-risk (SR) subgroup of acute lymphoblastic leukemia in adults (aALL) is a heterogeneous category, with a 20% to 40% relapse rate and a wide range of relapse-free survival (RFS) and overall survival (OS).There is a need to identify at the outset those patients with SR-aALL who are likely to have shorter RFS and OS, sothey can be treated more aggressively. Flow cytometric data of 81 patients with SR-aALL treated with astandardized protocol were retrospectively analyzed. Thirty-two patients (40%) relapsed; the median RFS and OS were12.5 months (range, 1-136 months) and 30 months (range, 3-235 months), respectively. Twenty-six patients survived≥48 months. Expression of myeloid antigen CD13, using the conventional≥ 20% threshold and alower≥ 5% threshold, was seen in 17 (29%) of 59 and 29 (49%) of 59 patients, respectively, whereas dual expression of CD13 and CD33 was seen in 8 patients. CD13 positivity at≥ 20% and≥ 5% threshold was associated with a shorter RFS (P= .0158 and P< .0001, respectively) and OS (P= .0072 and P< .0001, respectively). Dual expression of CD13 (at≥ 5% or≥ 20% threshold) and CD33 was associated with inferior OS (P= .0038 and P=.0032, respectively) and RFS (P= .0705 and P= .2516, respectively). For≥ 20% and≥ 5% threshold of positivity, 16 of 42 and 28 of 42 who survived< 48 months were positive, compared with 1 of 17 and 1 of 17 who survived≥ 48 months (P= .0133 and P< .0001, respectively). Aberrant expression of CD13 in≥ 5% of blasts of patients with SR-aALL is an adverse prognostic factor, delineating a subgroup of patients with SR-aALL that should be considered for more aggressive treatment.