GvHD prophylaxis in elderly patients: post-transplant cyclophosphamide or ATG? A study by the EBMT transplant complications working party.

Allogeneic hematopoietic cell transplantation (allo‑HCT) has become increasingly feasible in older patients with hematologic malignancies, yet the optimal graft‑versus‑host disease (GvHD) prophylaxis in this population remains uncertain. We compared post‑transplant cyclophosphamide (PTCy) with anti‑thymocyte globulin (ATG) in patients aged ≥60 years undergoing reduced‑intensity conditioning (RIC) peripheral blood stem cell allo‑HCT, using EBMT registry data from 2016 to 2022. A total of 7507 patients were included: 1418 matched sibling donors (MSD), 5051 matched unrelated donors (MUD), and 1038 mismatched unrelated donor (MMUD) transplants. In MSD recipients aged >65 years, PTCy was associated with reduced relapse, improved progression‑free survival (PFS), and superior GvHD‑ and relapse‑free survival (GRFS). However, in MSD recipients aged 60-65 years, these outcomes did not differ significantly between PTCy and ATG. Among MUD recipients, PTCy was associated with lower relapse and chronic GvHD, and a higher PFS, GRFS, and overall survival. In MMUD transplants, outcomes were not significantly different. Our findings indicate that PTCy is a safe and effective alternative to ATG in older allo‑HCT recipients, especially in MUD transplants and in MSD recipients aged >65 years, but the findings should be interpreted cautiously given their observational nature and patient heterogeneity. Further studies are warranted to assess long‑term outcomes.