Survival benefits from reduced-intensity conditioning in allogeneic stem cell transplantation for young lower-risk MDS patients without significant comorbidities

The aim of this study was to determine the optimum conditioning intensity for allogeneic stem cell transplantation (SCT) in young (age ≤50), lower-risk (INT-1 by IPSS) Myelodysplastic syndrome (MDS) patients without significant comorbidities (hematopoietic cell transplantation-comorbidity index score ≤3).Transplant outcomes from 46 consecutive patients were retrospectively analyzed according to the conditioning intensity: reduced-intensity conditioning (RIC; n = 14), intensified RIC by adding low-dose total body irradiation (iRIC; n = 15), and myeloablative conditioning (MAC; n = 17).After a median follow-up of 73.7 months, RIC had a better 4-yr overall survival (OS) (92.9%) compared with the iRIC (64.2%) or MAC (70.6%). Multivariate analysis showed that RIC was associated with improved OS compared with the MAC [relative risk (RR) of 0.08, P = 0.022] because of a lower transplant-related mortality (TRM) (RR, 0.08, P = 0.035). iRIC failed to show survival benefits over the MAC (RR of 0.77, P = 0.689) because of similarly high TRM (RR of 0.41, P = 0.480). Cumulative incidence of acute and chronic graft-versus-host disease (GVHD) after RIC was higher, but GVHD-specific survival was significantly better (RIC 100% vs. iRIC 45.7% vs. MAC, P = 0.018). Relapse rate was not different among the three groups, but in the RIC group, azacitidine was available and useful for inducing remission in two patients.This study shows that RIC improved OS by directly lowering TRM and indirectly giving an additional chance for relapsed MDS in the era of hypomethylating treatment. RIC-SCT should be considered for relative healthy lower-risk MDS patients.