Very long-term outcome of acute promyelocytic leukemia after treatment with all-trans retinoic acid and chemotherapy: the European APL Group experience.

Acute promyelocytic leukemia (APL) is highly curable with the combination of all-trans retinoic acid (ATRA) and anthracycline-based chemotherapy (CT), but very long-term results of this treatment, when CT should be added to ATRA and the role of maintenance treatment, remain uncertain. In our APL93 trial that included 576 newly diagnosed APL patients, with a median follow-up of 10 years, 10-year survival was 77%. Maintenance treatment significantly reduced 10-year cumulative incidence of relapses, from 43.2% to 33%, 23.4%, and 13.4% with no maintenance, maintenance using intermittent ATRA, continuous 6 mercaptopurine plus methotrexate, and both treatments, respectively (P < .001). Maintenance particularly benefited patients with white blood cell (WBC) count higher than 5 x 10(9)/L (5000/microL). Early addition of CT to ATRA significantly improved 10-year event-free survival (EFS), but without significant effect on overall survival (OS). The 10-year cumulative incidence of deaths in complete response (CR), resulting mainly from myelosuppression, was 5.7%, 15.4%, and 21.7% in patients younger than 55, 55 to 65, and older than 65 years, respectively, supporting the need for less myelosuppressive treatments, particularly for consolidation therapy. This study is registered at https://clinicaltrials.gov as NCT00599937.