The trial ALL-BFM 95 for treatment of childhood acute lymphoblastic leukemia was designed to reduce acute and long-term toxicity in selected patient groups with favorable prognosis and to improve outcome in poor-risk groups by treatment intensification. These aims were pursued through a stratification strategy using white blood cell count, age, immunophenotype, treatment response, and unfavorable genetic aberrations providing an excellent discrimination of risk groups. Estimated 6-year event-free survival (6y-pEFS) for all 2169 patients was 79.6% (+/- 0.9%). The large standard-risk (SR) group (35% of patients) achieved an excellent 6y-EFS of 89.5% (+/- 1.1%) despite significant reduction of anthracyclines. In the medium-risk (MR) group (53% of patients), 6y-pEFS was 79.7% (+/- 1.2%); no improvement was accomplished by the randomized use of additional intermediate-dose cytarabine after consolidation. Omission of preventive cranial irradiation in non-T-ALL MR patients was possible without significant reduction of EFS, although the incidence of central nervous system relapses increased. In the high-risk (HR) group (12% of patients), intensification of consolidation/reinduction treatment led to considerable improvement over the previous ALL-BFM trials yielding a 6y-pEFS of 49.2% (+/- 3.2%). Compared without previous trial ALL-BFM 90, consistently favorable results in non-HR patients were achieved with significant treatment reduction in the majority of these patients.
