Antithymocyte globulins and chronic graft-vs-host disease after myeloablative allogeneic stem cell transplantation from HLA-matched unrelated donors: a report from the Sociéte Française de Greffe de Moelle et de Thérapie Cellulaire.

This retrospective report assessed the impact of rabbit antithymocyte globulins (ATG), incorporated within a standard myeloablative conditioning regimen prior to allogeneic stem cell transplantation (allo-SCT) using human leukocyte antigen-matched unrelated donors (HLA-MUD), on the incidence of acute and chronic graft-vs-host disease (GVHD). In this series of leukemia patients, 120 patients (70%) did not receive ATG ('no-ATG' group), whereas 51 patients received ATG ('ATG' group). With a median follow-up of 30.3 months, the cumulative incidence of grade 3-4 acute GVHD was 36% in the no-ATG group and 20% in the ATG group (P = 0.11). The cumulative incidence of extensive chronic GVHD was significantly lower in the ATG group as compared to the no-ATG group (4 vs 32%, respectively; P = 0.0017). In multivariate analysis, the absence of use of ATG was the strongest parameter associated with an increased risk of extensive chronic GVHD (relative risk) = 7.14, 95% CI: 1.7-33.3, P = 0.008). At 2 years, the probability of nonrelapse mortality, relapse, overall and leukemia-free survivals was not significantly different between the no-ATG and ATG groups. We conclude that the addition of ATG to GVHD prophylaxis resulted in decreased incidence of extensive chronic GVHD without an increase in relapse or nonrelapse mortality, and without compromising survival after myeloablative allo-SCT from HLA-MUD.