Lower dose of antithymocyte globulin does not increase graft-versus-host disease in patients undergoing reduced-intensity conditioning allogeneic hematopoietic stem cell transplant.

The appropriate dose of antithymocyte globulin (ATG) to be utilized in reduced-intensity conditioning (RIC) allogeneic hematopoietic stem cell transplant (alloHSCT) is as yet unknown. We retrospectively compared patients who received 7.5 mg/kg (R-ATG, 39 patients) and 6 mg/kg (r-ATG, 97 patients). The cumulative incidences of acute graft-versus-host disease (aGVHD) grade II-IV at 180 days were 46% and 41% and of aGVHD grade III-IV were 11% and 18% in r-ATG and R-ATG, respectively (p > 0.30). The respective estimated cumulative incidences at 24 months of cGVHD were 42% and 44% (p > 0.30). There was no significant difference in non-relapse mortality (p = 0.22), cumulative incidence of relapse (p = 0.53), progression-free survival (p = 0.69) or overall survival (p = 0.95). In conclusion, a decreased ATG dose of 6 mg/kg was associated with a similar proportion of GVHD to 7.5 mg/kg ATG. Given the increasing number of RIC HSCTs performed worldwide, the correct dose and preparation of ATG should be defined by prospective randomized trials.