S Kayser, J Krzykalla, M A Elliott, K Norsworthy, P Gonzales, R K Hills, M R Baer, Z Ráčil, J Mayer, J Novak, P Žák, T Szotkowski, D Grimwade, N H Russell, R B Walter, E H Estey, J Westermann, M Görner, A Benner, A Krämer, B D Smith, A K Burnett, C Thiede, C Röllig, A D Ho, G Ehninger, R F Schlenk, M S Tallman, M J Levis, U Platzbecker

Therapy-related acute promyelocytic leukemia (t-APL) is relatively rare, with limited data on outcome after treatment with arsenic trioxide (ATO) compared to standard intensive chemotherapy (CTX). We evaluated 103 adult t-APL patients undergoing treatment with all-trans retinoic acid (ATRA) alone (n=7) or in combination with ATO (n=24), CTX (n=53), or both (n=19). Complete remissions were achieved after induction therapy in 57% with ATRA, 100% with ATO/ATRA, 78% with CTX/ATRA, and 95% with CTX/ATO/ATRA. Early death rates were 43% for ATRA, 0% for ATO/ATRA, 12% for CTX/ATRA, and 5% for CTX/ATO/ATRA. Three patients relapsed, two developed therapy-related acute myeloid leukemia and 13 died in remission including seven patients with recurrence of the prior malignancy. Median follow-up for survival was 3.7 years. None of the patients treated with ATRA alone survived beyond one year. Event-free survival was significantly higher after ATO-based therapy (95%, 95%-CI, 82-99%) as compared to CTX/ATRA (78%, 95%-CI, 64-87%; P=0.042), if deaths due to recurrence of the prior malignancy were censored. The estimated 2-year overall survival in intensively treated patients was 88% (95%-CI, 80-93%) without difference according to treatment (P=0.47). ATO when added to ATRA or CTX/ATRA is feasible and leads to better outcomes as compared to CTX/ATRA in t-APL.Leukemia accepted article preview online, 21 March 2017. doi:10.1038/leu.2017.92.