Impact of low-dose rabbit anti-thymocyte globulin in unrelated hematopoietic stem cell transplantation.

We retrospectively evaluated the outcome of administering low-dose rabbit anti-thymocyte globulin (thymoglobulin: ATG-T) to 219 patients (ATG-T group, n = 30; no-ATG-T group, n = 189) who received an initial unrelated hematopoietic stem cell transplantation (uHSCT). The median total dose of ATG-T was 1.5 mg/kg. There was no significant difference in the cumulative incidences of grade II-IV (42 vs. 38 %, P = 0.87) and grade III-IV (5 vs. 7 %, P = 0.52) acute GVHD. In patients who received uHSCT from a donor with at least one HLA allele mismatch, the cumulative incidence of extensive chronic GVHD was significantly lower in the ATG-T group than that in the no-ATG-T group (13 vs. 44 %, P = 0.02). No patient in the ATG-T group developed chronic lung dysfunction. The probabilities of 1-year, GVHD-free/relapse-free survival (GRFS) were 61 % in the ATG-T group and 35 % in the no-ATG-T group (P = 0.02). Patients in the ATG-T group discontinued immunosuppressive drugs significantly earlier than those in the no-ATG-T group (P < 0.01). The use of low-dose ATG-T did not increase the incidence of severe infectious disease. The use of low-dose ATG-T in patients who received uHSCT was associated with a superior GRFS, reflecting the reduced incidence of severe/persistent GVHD without compromising overall survival.