Retinoic acid and arsenic trioxide for acute promyelocytic leukemia

BACKGROUND: All-trans retinoic acid (ATRA) with chemotherapy is the standard of care for acute promyelocytic leukemia (APL), resulting in cure rates exceeding 80%. Pilot studies of treatment with arsenic trioxide with or without ATRA have shown high efficacy and reduced hematologic toxicity. METHODS: We conducted a phase 3, multicenter trial comparing ATRA plus chemotherapy with ATRA plus arsenic trioxide in patients with APL classified as low-to-intermediate risk (white-cell count, ≤10×109per liter). Patients were randomly assigned to receive either ATRA plus arsenic trioxide for induction and consolidation therapy or standard ATRA- idarubicin induction therapy followed by three cycles of consolidation therapy with ATRA plus chemotherapy and maintenance therapy with low-dose chemotherapy and ATRA. The study was designed as a noninferiority trial to show that the difference between the rates of event-free survival at 2 years in the two groups was not greater than 5%. RESULTS: Complete remission was achieved in all 77 patients in the ATRA-arsenic trioxide group who could be evaluated (100%) and in 75 of 79 patients in the ATRA-chemotherapy group (95%) (P = 0.12). The median follow-up was 34.4 months. Two-year event-free survival rates were 97% in the ATRA-arsenic trioxide group and 86% in the ATRA-chemotherapy group (95% confidence interval for the difference, 2 to 22 percentage points; P<0.001 for noninferiority and P = 0.02 for superiority of ATRA-arsenic trioxide). Overall survival was also better with ATRA-arsenic trioxide (P = 0.02). As compared with ATRA-chemotherapy, ATRA-arsenic trioxide was associated with less hematologic toxicity and fewer infections but with more hepatic toxicity. CONCLUSIONS: ATRA plus arsenic trioxide is at least not inferior and may be superior to ATRA plus chemotherapy in the treatment of patients with low-to-intermediate-risk APL.