Post-Transplantation Cyclophosphamide-Based Graft-versus-Host Disease Prophylaxis in HLA-Matched and Haploidentical Donor Transplantation for Patients with Hodgkin Lymphoma: A Comparative Study of the Lymphoma Working Party of the European Society for Blood and Marrow Transplantation.

INTRODUCTION Post-transplant cyclophosphamide (PTCy) has proven to be a highly effective strategy in preventing graft-versus-host disease (GVHD) in haploidentical (haplo) hematopoietic stem cell transplantation (HSCT), but it is being increasingly used in HLA-matched transplants. The outcomes of haplo HSCT with PTCY in various hematologic malignancies, particularly in relapsed/refractory Hodgkin disease (HD), have shown promising results, challenging those obtained in transplant patients from HLA-matched donors without PTCy. However, there is limited information on the impact of donor types on the outcomes of patients with HD undergoing allogenic HSCT when using homogeneous GVHD prophylaxis with PTCy. To address this knowledge gap, we have conducted an extensive study using the Lymphoma Working Party of the European Society for Blood and Marrow Transplantation (LWP-EBMT) registry. The aim of this study was to compare the outcomes of patients with HD undergoing HSCT from both HLA-matched donors, which include matched sibling donors (MSD) and matched unrelated donors (MUD), and haplo donors, using PTCy as GVHD prophylaxis approach in all cohorts. PATIENTS AND METHODS Inclusion criteria All adults (≥ 18 years) patients diagnosed with HD who underwent their first HSCT between January 2010 and December 2020 from either a MSD, MUD or haplo, and whose data were reported to the EBMT registry were included. For the purposes of this study, only transplants who received PTCy-based as GVHD prophylaxis were considered. Statistical Analysis The study utilized statistical methods such as Kaplan-Meier estimation, Log-Rank test, competing risks analysis, and Cox proportional hazards regression. The analyses included OS, PFS, NRM, aGVHD, cGVHD, and graft failure. The statistical software R and packages were used. RESULTS Patient and Transplantation Characteristics Patient, disease and transplant-related characteristics of the 860 patients are summarized in Table 1. Engraftment The cumulative incidence (Cum Inc) of neutrophil recovery at day 30 was 95% (95% CI, 93-96) in the HLA-matched group and 96% (95% CI, 91-98) in the haplo cohort (p=0.18). The 60-day Cum Inc of platelet recovery in similar order was 94% (95% CI, 88-97) and 86% (95% CI, 83-88) (p<0.001). GVHD The Cum Inc of acute GVHD grade II-IV at 100 days in the HLA-matched and the haplo cohorts was 24% (95% CI, 17-31) and 34% (95% CI, 30-37), respectively (p=0.01), whereas for grade III-IV it was 8% (95% CI, 4-13) and 10% (95% CI, 8-13), (p=0.44). In multivariable analysis (table 2), haplo was associated with an increased risk of acute GVHD grades II-IV, when compared with HLA-matched (HR 0.65; 95% CI, 0.46-0.93; p=0.01). Other variables are shown in table 2. The 2-year Cum Inc of chronic GVHD in the HLA-matched and haplo cohorts was 26% (95% CI, 19-33) and 27% (95% CI, 24-31), respectively (p=0.75). Other variables are shown in table 2. NRM and relapse The Cum Inc of NRM at 2 years was 10% (95% CI; 6-16) for HLA-matched and 18% (95% CI; 15-21) for haplo (p=0.02). In multivariable analysis (table 2), haplo was associated with an increased risk of NRM, when compared to HLA-matched (HR 0.5; 95% CI, 0.28-0.89; p=0.01). Other variables are shown in table 2. The Cum Inc of relapse at 2 years was 22% (95% CI; 15-29) for HLA-matched and 24% (95% CI; 20-27) for haplo (p=0.81). Other variables are shown in table 2. Survival The 2-year OS for the HLA-matched and haplo cohorts was 82% (95% CI; 75-88) and 70% (95% CI; 67-74), respectively (p=0.002). In multivariable analysis (table 2), compared to HLA-matched, haplo (HR, 0.51; 95% CI, 0.34-0.77; p=0.001) was associated with worse survival. Other variables are shown in table 2. The 2-year PFS was similar between HLA-matched and haplo (66%; 95% CI, 58-74; and 58%; 95% CI, 54-62, respectively; p=0.17). Other variables are shown in table 2. Comparison of outcomes for MSD and MUD With regards to the donor type, most posttransplant outcomes did not exhibit significant differences, except for a higher incidence of grades II-IV acute GVHD in the MUD group (33%; 95% CI, 32-44) compared to the MSD group (17%; 95% CI, 10-25) (p=0.01). CONCLUSION Our study shows that in patients with HD undergoing HSCT with PTCy for GVHD prophylaxis, no significant differences in 2-year PFS were observed between HLA-matched and haplo. A higher risk of acute GVHD and NRM is associated with haplo, leading to lower OS compared to HLA-matched transplantation.