Risk-adapted treatment of acute promyelocytic leukemia: results from International Consortium for Childhood APL

Pediatric acute promyelocytic leukemia (APL), a rare childhood neoplasm, can be cured with all-trans retinoic acid (ATRA) and anthracycline. However, most published trials to date have employed high cumulative doses of anthracyclines. Here, we report the outcome of patients with newly diagnosed APL enrolled into the International Consortium for Childhood APL (ICC-APL-01) trial, which reduced anthracycline exposure but extended that of ATRA. The study recruited 258 children/adolescents with molecularly/cytogenetically-proven APL. Patients were stratified into standard-risk (SR) and high-risk (HR) according to the baseline WBC count (< or ≥10x109/L); both groups received identical induction treatment with ATRA (25 mg/m2/day, for 30 consecutive days) and 3 doses of idarubicin (12 mg/m2/dose). Two or three blocks of consolidation therapy were administered to SR and HR patients, respectively, while maintenance therapy with low-dose chemotherapy and ATRA cycles was given to all patients for 2 years. The cumulative dose of daunorubicin-equivalent anthracyclines in SR and HR patients was lower than that of previous studies, being 355 mg/m2 and 405 mg/m2 in SR and HR patients, respectively. Hematologic remission was obtained in 97% of patients; 8 children died of intracranial hemorrhage in the first 2 weeks following diagnosis. The 5-year overall and event-free survival for the whole cohort were 94.6% and 79.9%, respectively; they were 98.4% and 89.4% in SR and 84.3% and 74.2% in HR patients (p=0.002 and p=0.043, respectively). These data demonstrate that extended use of ATRA coupled to a risk-adapted consolidation can achieve high cure rates in childhood APL and limit anthracycline exposure. The trial was registered at www.clinicaltrials.gov with the following identification number EudractCT 2008-002311-40.