Role of hematopoietic stem cell transplantation for relapsed acute promyelocytic leukemia: A retrospective analysis of JALSG-APL97

For patients with relapsed acute promyelocytic leukemia (APL), all-trans retinoic acid-based salvage regimens can achieve second complete remission (CR2), but the optimal post-remission strategy for APL patients after CR2 remains unclear. Hematopoietic stem cell transplantation (HSCT) during CR2 might be effective, but data on the role of HSCT for APL patients after CR2 are limited in Japan. We retrospectively analyzed outcomes for 57 relapsed APL patients who achieved CR2 in the JALSG APL97 study. Of those, six received autologous (auto)-HSCT, 21 received allogeneic (allo)-HSCT, and 30 received various regimens other than HSCT. The 5-year event-free survival (EFS) rate, overall survival (OS) rate and cumulative incidence of relapse (CIR) were 50.7%, 77.4% and 51.0% in the non-HSCT group, 41.7%, 83.3% and 58.3% in the auto-HSCT group and 71.1%, 76.2% and 9.8% in the allo-HSCT group, respectively. Both the EFS rate and CIR were significantly better in the allo-HSCT group than in other groups. Allo-HSCT appears effective in APL patients in CR2, with a low relapse rate beyond a relatively early transplantation-related mortality (19%). Among older patients (age ≥40 years), the 5-year OS was significantly better in the non-HSCT group than in the HSCT group (78.0% vs 40.5%; P = 0.04). Further prospective studies with larger patient numbers are required to confirm the impact of HSCT alone and in combination with arsenic trioxide on outcomes for patients with APL in CR2.