Post-transplant cyclophosphamide combined with anti-thymocyte globulin for graft-vs-host disease prophylaxis improves survival and lowers non-relapse mortality in older patients undergoing allogeneic hematopoietic cell transplantation

Graft-versus-host disease (GVHD) represents a major contributor to morbidity and mortality in recipients of allogeneic hematopoietic cell transplants (HCT). Several strategies exist for GVHD prophylaxis and include post-transplant cyclophosphamide (PTCY) and anti-thymocyte globulin (ATG). While several groups have described the use of PTCY in younger patients, there is a paucity of data about the efficacy of PTCY in older individuals, particularly when combined with ATG. We investigated the effect of PTCY and ATG combination on transplant outcomes in older patients at Princess Margaret Cancer Centre, Toronto, Canada. Compared to those patients who received other forms of GVHD prophylaxis, individuals who received ATG-PTCY combination had higher 2-year overall survival (OS), 57% (95% confidence interval, 44-69) vs 37% (26-49), P = 0.02; higher 2-year graft-vs-host- and relapse-free survival (GRFS), 27% (17-39) vs 12% (6-21), P = 0.01; lower 2-year non-relapse mortality (NRM), 21% (12-32) vs 45% (33-56), P = 1.00 x 10(-3); lower 100-day incidence of grade 2-4 acute GVHD (aGVHD), 11% (5-21) vs 28% (18-39), P = 0.02; and lower 100-day incidence of grade 3-4 aGVHD, 0% vs 7% (3-15), P = 0.02 without an increase in the 2-year cumulative incidence of relapse (CIR), 31% (20-43) vs 21% (12-32), P = 0.14. Therefore, in older HCT recipients, use of PTCY combined with ATG is associated with improved OS, lower NRM, decreased risk of aGVHD, and improved GRFS without a significant increase in relapse risk. Therefore, the PTCY with ATG combination represents an effective strategy for GVHD prophylaxis in older allogeneic HCT recipients.