Background: Allogeneic peripheral-blood stem-cell transplantation (SCT) from a matched related donor after myeloablative conditioning is the preferred curative treatment for patients with high-risk blood cancers. The combination of a calcineurin inhibitor and an antimetabolite remains standard care for graft-versus-host disease (GVHD) prophylaxis in these patients. Data from two randomized trials have suggested that post-transplantation cyclophosphamide can reduce the risk of GVHD after SCT from a matched donor when it is added to or replaces the antimetabolite. However, the effects of post-transplantation cyclophosphamide specifically after SCT from a matched related donor remain uncertain, and effects in the context of myeloablative conditioning are unclear.
Methods: We randomly assigned adults who were undergoing SCT from a matched related donor after myeloablative or reduced-intensity conditioning to receive either post-transplantation cyclophosphamide-cyclosporin (experimental prophylaxis) or cyclosporin-methotrexate (standard prophylaxis). The primary end point was GVHD-free, relapse-free survival.
Results: Among 134 patients who underwent randomization, 66 were assigned to receive experimental prophylaxis and 68 to receive standard prophylaxis. GVHD-free, relapse-free survival was significantly longer with experimental prophylaxis (median, 26.2 months; 95% confidence interval [CI], 9.1 to not reached) than with standard prophylaxis (median, 6.4 months; 95% CI, 5.6 to 8.3; P<0.001 by a log-rank test). GVHD-free, relapse-free survival at 3 years was 49% (95% CI, 36 to 61) with experimental prophylaxis and 14% (95% CI, 6 to 25) with standard prophylaxis (hazard ratio for GVHD, relapse, or death, 0.42; 95% CI, 0.27 to 0.66). The cumulative incidence of grade III to IV acute GVHD at 3 months was 3% (95% CI, 1 to 10) in the experimental-prophylaxis group and 10% (95% CI, 4 to 19) in the standard-prophylaxis group. At 2 years, overall survival was 83% and 71%, respectively (hazard ratio for death, 0.59; 95% CI, 0.29 to 1.19). The incidence of serious adverse events was similar in the two groups in the first 100 days after SCT.
Conclusions: The combination of post-transplantation cyclophosphamide and a calcineurin inhibitor led to longer GVHD-free, relapse-free survival than standard prophylaxis after transplantation from a matched related donor with either reduced-intensity or myeloablative conditioning in patients with blood cancers. (Funded by the Australian Government Medical Research Future Fund and others; ALLG BM12 CAST Australian-New Zealand Clinical Trials Registry number, ACTRN12618000505202.).
Copyright © 2025 Massachusetts Medical Society.