[en] BACKGROUND: It is unknown whether the duration of systemic immunosuppressive treatment after allogeneic nonmyeloablative hematopoietic cell transplantation (HCT) might influence the incidence, severity, timing, and/or corticosteroid-responsiveness of graft-versus-host disease (GVHD). METHODS: We retrospectively analyzed outcomes among 185 patients with hematologic malignancies who were given grafts from HLA-matched related donors following conditioning with 2 Gy total body irradiation alone or in combination with fludarabine between December 1998 and March 2003. Postgrafting immunosuppression consisted of mycophenolate mofetil (days 0-27) in combination with 3 different cyclosporine (CSP) regimens: taper from (A) days 35 to 56 (n=107), (B) days 56 to 77 (n=35), and (C) days 56 to 180 (n=43). RESULTS: The overall incidences of grades II-IV and III-IV acute GVHD, and extensive chronic GVHD were 52%, 13%, and 56%, respectively. The duration of CSP prophylaxis did not significantly influence the overall rate of acute GVHD (grade II-IV), extensive chronic GVHD, or non-relapse mortality. However, prolonged administration of CSP (group C) was associated with a significantly decreased hazard of grades III-IV acute GVHD (HR 0.2, 95% CI [0.04, 0.9]) and with an increased likelihood of discontinuing all systemic immunosuppression (HR 2.4, 95% CI [1.1, 5.2]) when compared to the shortest course of CSP (group A). CONCLUSION: Longer CSP duration decreased the risk of severe GVHD and increased the likelihood of discontinuing all systemic immunosuppression after nonmyeloablative HCT with HLA-matched related grafts.