Outcomes of Allogeneic Stem Cell Transplant in Patients with Relapsed/Refractory Hodgkin Lymphoma

BACKGROUND: The aim of this study was to evaluate real-world clinical outcomes and transplant-related complications of allogeneic stem cell transplantation (alloSCT) for Hodgkin lymphoma (HL). METHODS: This was a single-centre, retrospective analysis of relapsed and refractory (R/R) HL patients who received an alloSCT between 1 January 2016 and 29 February 2024 in Hamilton, Ontario. The primary endpoint was overall survival (OS). The secondary endpoints were progression-free survival (PFS), non-relapse mortality (NRM), and graft-versus-host disease/relapse-free survival (GRFS). RESULTS: Twenty-one patients were identified, with thirteen (62%) pre-treated with programmed death 1 (PD-1) blockade with either nivolumab or pembrolizumab. Seventeen (81%) patients underwent related haploidentical donor transplants, while four (19%) patients received a matched unrelated donor transplant. The 2-year OS and PFS rates were 79% (95% CI: 53-92%) and 63% (95% CI: 37-81%), respectively. Trends towards improved OS, PFS, NRM, and GRFS in PD-1-inhibitor-exposed patients were observed. All PD-1-inhibitor-exposed patients who were in complete remission proceeding to alloSCT remained alive at the last follow-up visit. Among the nine patients in partial remission at the time of alloSCT, three deaths were reported, with a 2-year OS of 61%. CONCLUSIONS: Our outcome data of a single-centre, heavily pre-treated cohort of Canadian patients confirm that alloSCT with post-transplant cyclophosphamide-based immunosuppression, which has been associated with improvements in PFS, remains a safe and feasible treatment option for patients with R/R HL in the era of checkpoint inhibitor use.