Unrelated donor transplant recipients given Thymoglobuline have superior GRFS when compared to matched related donor recipients transplanted without ATG.

Abstract Recipients of allogeneic hematopoietic stem cell transplantation (HSCT) from unrelated (URD) and mismatched related donors (MMRD) typically have a higher incidence of acute and chronic graft-versus-host disease (GVHD) compared to matched related donors (MRD). Anti-T-cell globulins (ATG) are often used to reduce GVHD in these recipients. We report the outcomes of 211 adult peripheral blood stem cell transplant recipients with myeloid malignancies who received a standardized transplant protocol, in which ATG (Thymoglobuline 4.5mg/kg) was administered to recipients of URD and MMRD (n=147) but not MRD (n=64) transplant. For all patients, incidence of acute GVHD grades 2–4 was 21.4%, and chronic GVHD was 35.0%. Two-year overall survival was 63.2% (95% CI 55.8%–71.5%), relapse-free survival 55.3% (47.4%–64.6%) and GVHD-free, relapse-free survival (GRFS) was 30.7% (23.2%–40.8%). There were no differences between recipients of MRD and other donors in relapse, non-relapse mortality, overall and relapse-free survival. However, compared to MRD, recipients from URD and MMRD had reduced moderate-severe chronic GVHD (10.4% vs. 30.1%, p=0.002), less chronic GVHD requiring systemic therapy (19.4% vs. 38.9%, p=0.006) and superior 2-year GRFS (35.5% vs. 20.0%, p=0.003). In this retrospective review of non-randomized transplant groups, outcomes of HSCT performed using an URD with ATG during conditioning were superior to transplant from a MRD without ATG. The addition of Thymoglobuline to conditioning in HSCT from MRD should be further examined in prospective trials.