PTCY and Tacrolimus for GVHD Prevention for Older Adults Undergoing HLA-Matched Sibling and Unrelated Donor AlloHCT

The use of post-transplantation cyclophosphamide (PTCY) for graft-versus-host disease (GHVD) prevention is becoming prevalent in the transplantation community when HLA-identical sibling and 10/10 HLA-matched (MUD) and 9/10 mismatched unrelated donors are selected for alloHSCT. However, reported evidence on outcomes from elderly patients receiving PTCY-containing GVHD prophylaxis remains limited. This study aims to compare the outcomes of PTCY- tacrolimus (TK) prophylaxis and conventional GVHD prophylaxis in patients aged >50 years undergoing peripheral blood alloHSCT from a single institution. A total of 161 consecutive patients aged >50 years undergoing alloHSCT between January 2014 and February 2021 were included. Data were collected retrospectively and updated in December 2021. Patients received grafts from HLA-identical sibling, and from 10/10 and 9/10 HLA matched and mismatched unrelated donors. Overall, median age was 60 years, and 91 (54.8%) received PTCY-TK for GVHD prevention. Time to neutrophil and platelet engraftment was longer in the PTCY-TK group (20 versus 16 days and 19 versus 11 days, P < .001). The cumulative incidences of grade II-IV and III-IV acute GVHD (aGVHD) at day 100 and moderate/severe chronic GVHD (cGVHD) at 2 years were 18.2%, 5.7%, and 9.5% for patients receiving PTCY-TK, and 26.0%, 9.6% and 39.5% for those who did not. The multivariate analysis showed that PTCY-TK reduced the probability of grade II-IV aGVHD (hazard ratio [HR] 0.41, P = .035), of cGVHD (any grade: HR 0.43 [P = .014], and of moderate/severe cGVHD [HR 0.15 {P < .001}]). At 2 years, the overall survival (65.4% versus 65.6%, P = .472), non-relapse mortality (17.4% versus 13.7%, P = .967), and cumulative incidence of relapse rates (24.2% versus 27.5%, P = .712) were comparable between both cohorts; GVHD-free/relapse-free survival (GRFS) was higher in the PTCY-TK group (2 years: 50.2% versus 21.8%; HR 0.42, P = .001). In patients aged ≥50 years. PTCY-TK was safe and a more effective drug combination than non-PTCY containing GVHD prophylaxis, even with the use of matched and mismatched unrelated donors, and resulted in comparable relapse rates and better GRFS.