Intensified chemotherapy without SCT in infant ALL: Results from COG P9407 (Cohort 3)

Abstract

Background Infants with acute lymphoblastic leukemia (ALL) present with aggressive disease and a poor prognosis. Early relapse within 6–9 months of diagnosis is common. Approximately 75% of infants have MLL‐rearranged (MLL‐R) ALL with event free survival (EFS) ranging from 20% to 30%. Children's Oncology Group (COG) P9407 used shortened (46 weeks), intensified therapy to address early relapse and poor EFS. Procedure P9407 therapy was modified three times for induction toxicity resulting in three cohorts of therapy. One hundred forty‐seven infants were enrolled in the third cohort. Results We report an overall 5‐year EFS and OS of 42.3 ± 6% and 52.9 ± 6.5% respectively. Poor prognostic factors included age ≤90 days at diagnosis, MLL‐R ALL and white cell count ≥50,000/μl. For infants ≤90 days of age, the 5‐year EFS was 15.5 ± 10.1% and 48.5 ± 6.7% for those >90 days (P < 0.0001). Among infants >90 days of age, 5‐year EFS rates were 43.8 ± 8% for MLL‐R versus 69.1 ± 13.6% for MLL‐germline ALL (P < 0.0001). Conclusions Age ≤90 days at diagnosis was the most important prognostic factor. Despite shortened therapy with early intensification, EFS remained less than 50% overall in MLL‐R ALL. Pediatr Blood Cancer 2015;62:419–426.