Safety and efficacy of immune checkpoint inhibitors as a bridge to allogeneic hematopoietic stem cell transplantation in classical Hodgkin lymphoma: A systematic review and meta-analysis.

Abstract

Immune checkpoint inhibitors (ICIs) have transformed the treatment landscape for relapsed or refractory classical Hodgkin lymphoma (cHL); however, a substantial subset of patients ultimately requires allogeneic hematopoietic stem cell transplantation (allo-HCT) to achieve long-lasting disease control. The use of ICIs as a bridge to allo-HCT has therefore gained increasing clinical interest, though concerns persist regarding post-transplant complications and incompletely-defined safety profiles. Accordingly, this systematic review and meta-analysis was conducted to evaluate outcomes of ICIs administered prior to allo-HCT in cHL. Following PRISMA guidelines, a comprehensive literature search was conducted across online databases through January 2026. Eligible studies included observational designs reporting survival and transplant-related outcomes in cHL patients treated with ICIs followed by allo-HCT. Pooled proportions for overall survival, progression-free survival, non-relapse mortality, and graft-versus-host disease (GVHD) incidence were calculated using a random-effects model. Seven studies comprising 739 patients were included. Post-transplant survival outcomes were favorable, with high pooled estimates across timepoints. Transplant-related mortality remained low, with NRM rates consistently within an acceptable range through long-term follow-up. Acute GVHD was observed at a meaningful frequency, including a smaller subset of severe cases, while chronic GVHD occurred in approximately one-quarter of patients at follow-up. Overall, these findings suggest that ICI therapy prior to allo-HCT in cHL is associated with encouraging survival and disease control and does not appear to confer excessive non-relapse mortality, supporting its use as a feasible and effective bridging strategy, while underscoring the need for future prospective studies to clarify optimal timing, risk mitigation strategies, and patient selection.