Impact of post-transplant cyclophosphamide (PTCy)-based prophylaxis in matched sibling donor allogeneic haematopoietic cell transplantation for patients with myelodysplastic syndrome: a retrospective study on behalf of the Chronic Malignancies Working Party of the EBMT.

We retrospectively compared outcomes of 404 MDS patients undergoing 1st matched sibling donor allo-HCT receiving either PTCy-based (n = 66) or other "conventional prophylaxis" (n = 338; mostly calcineurin inhibitor + methotrexate or MMF). Baseline characteristics were balanced, except for higher use of myeloablative regimens in the PTCy group (52.3% vs. 38.2%, p = 0.047). Incidences of neutrophil (Day +28: 89% vs. 97%, p = 0.011) and platelet (Day +100: 89% vs. 97%, p < 0.001) engraftment were lower for PTCy-based. Day +100 cumulative incidences of grade II-IV and III-IV aGVHD, and 5-year CI of extensive cGVHD were 32%, 18% and 18% for PTCy-based and 25% (p = 0.3), 13% (p = 0.4) and 31% (p = 0.09) for the conventional cohort. Five-year OS (51% vs. 52%, p = 0.6) and GRFS (33% vs. 25%, p = 0.6) were similar between groups. Patients receiving PTCy had a trend to a lower cumulative incidence of relapse (20% vs. 33%, p = 0.06), not confirmed on multivariable analysis (p = 0.3). Although higher NRM rates were observed in patients receiving PTCy (32% vs. 21%, p = 0.02) on univariate analysis, this was not confirmed on multivariate analysis (HR 1.46, p = 0.18), and there was no resultant effect on OS (HR 1.20, p = 0.5). Based on these data, PTCy prophylaxis appears to be an attractive option for patients with MDS undergoing MSD allo-HCT.