Outcomes of Allogeneic HCT in Hodgkin Lymphoma in the Era of Checkpoint Inhibitors: A Joint CIBMTR and EBMT Analysis. Available to Purchase

• Prior exposure to CPI is associated with increased PFS due to decreased incidence of relapse after HCT, suggesting an increased GVL.

• PTCy based GVHD prophylaxis resulted in improved OS, lower grade II-IV acute GVHD and chronic GVHD in patients with prior CPI exposure.

Checkpoint inhibitors (CPI) have shown remarkable efficacy in patients with Hodgkin lymphoma (HL) and are now used routinely for this disease. While allogeneic hematopoietic cell transplantation (alloHCT) remains a curative option for HL, there are concerns that prior CPI may exacerbate post alloHCT complications, particularly graft-versus-host disease (GVHD), and lead to worse outcomes. Given the relative paucity of data, we performed a CIBMTR/EBMT study to examine the impact of prior CPI in alloHCT outcomes. We included 2186 adult patients > 18 years who received a first alloHCT using a matched related, unrelated or haploidentical donor from 2008-2023. Twenty-seven percent of patients received prior CPI. GVHD prophylaxis was post-transplant cyclophosphamide in 55.8% patients in the CPI cohort and 35% in the non-CPI cohort. Median follow-up among survivors was longer for the non-CPI (39 months) than CPI cohort (16.5 months). In the multivariate analysis, prior CPI exposure did not affect overall survival or non-relapse mortality but resulted in improved progression-free survival (non-CPI vs. CPI HR 0.81, 0.67-0.98, p=0.03) and lower incidence of relapse (HR 0.58, 0.45-0.76, p<0001). While grade II-IV (HR1.26, 1.04-1.53; p=0.02) and III-IV (HR1.41, 1.04-1.92; p=0.03) acute GVHD were increased differences in chronic GVHD were not significant. Use of post-transplant cyclophosphamide based GVHD prophylaxis resulted in improved OS, lower grade II-IV acute GVHD and chronic GVHD in patients with prior CPI exposure. In summary, allo-HCT should still be considered a curative option for patients with HL in the era of checkpoint inhibitors.