Outcome of Acute Promyelocytic Leukemia (APL) in Children and Adolescents: An Analysis in Two Consecutive Trials of the European APL Group

Abstract

Acute promyelocytic leukemia (APL) is rare in children. All-trans-retinoic acid (ATRA) combined with chemotherapy, the reference treatment of APL, is generally considered to produce similar results in children and adults. However, previously published childhood APL studies have generally analyzed all patients age < 18 years as a group, without further dividing according to age. We compared disease characteristics and outcomes of children (age ≤ 12 years), adolescents (13 to 18 years), and adults (> 18 years) included in two multicenter APL clinical trials (APL 93 and 2000 trials). Of the 833 patients age ≤ 60 years included in the two trials, 26 (3%), 58 (7%), and 749 (90%) were children, adolescents, and adults, respectively. Children had significantly higher baseline WBC counts (P < .001). The complete remission (CR) rate (92%, 100%, and 94.5%, respectively) and 5-year cumulative incidence of relapse (CIR; 28%, 20%, and 23%, respectively) did not differ between children, adolescents, and adults, whereas adolescents had significantly better overall survival (OS; 5-year OS, 93.6% v 80.4% in adults and 80.4% in children; P = .03). However, in children age ≤ 4 years, the 5-year CIR was 52%, compared with 17.6% in children age 5 to 12 years (P = .006), although most of the younger children who relapsed experienced durable salvage with autologous or allogeneic stem-cell transplantation. Adolescents and children age > 4 years with APL treated with ATRA and chemotherapy have outcomes at least as favorable as those of adults. Younger children seem to experience more relapses and may require reinforcement of first-line treatment.