Prophylaxis with sirolimus and tacrolimus ± antithymocyte globulin reduces the risk of acute graft-versus-host disease without an overall survival benefit following allogeneic stem cell transplantation.

Methotrexate (MTX) is a standard agent used in combination with calcineurin inhibitors for graft-versus-host disease (GVHD) prophylaxis in patients undergoing allogeneic hematopoietic cell (HCT) transplantation. We retrospectively compared the incidence of acute GVHD (aGVHD), transplant-related morbidity, and mortality in patients given sirolimus/tacrolimus ± antithymocyte globulin (ATG) versus MTX/tacrolimus or cyclosporine and allogeneic transplantation for hematologic malignancies. Between January 1, 2005, and April 30, 2009, 106 consecutive patients received peripheral blood HCT or bone marrow grafts after 1 of 6 myeloablative conditioning regimens. The incidence of grade II-IV aGVHD was 18.6% in patients who received sirolimus/tacrolimus compared to 48.9% who received MTX (P = .001). The incidence of grade III-IV aGVHD was 5% and 17% (P = .045), respectively. There was no difference in overall survival (OS) between the groups (P = .160). Chronic GVHD (cGVHD) occurred in 40.4% who received sirolimus and 41.9% receiving MTX (P = .89). The incidence of thrombotic microangiopathy or interstitial pneumonitis was not significantly different between groups. The reduction in the risk of severe aGVHD was offset by an increased (20% versus 4%, P = .015) incidence of and mortality from sinusoidal obstructive syndrome (SOS). Sirolimus/tacrolimus appears to reduce the incidence of aGVHD after conventional allotransplantion compared to MTX-calcineurin inhibitor prophylaxis; however, this did not improve survival.