Overall survival after post-transplant cyclophosphamide (PTCy) peripheral blood hematopoietic cell transplantation (HCT) differs by race, ethnicity, and donor

Abstract Introduction Hispanic and non-Hispanic Black (NHB) patients have worse HCT survival compared to non-Hispanic White (NHW) patients and were less likely to utilize an unrelated HCT donor (Khera et al. Blood Adv. 2024; Hahn et al. JAMA Netw Open. 2024), but this difference has not been evaluated in the PTCy era. PTCy reduces graft-versus-host disease (GvHD) and allows for increased availability of allogeneic donors in minority patients. It is important to know the best donor source for each ethnicity. In this study, we investigated the association of race/ethnicity and donor type on overall survival (OS). Methods We performed a secondary analysis of adult patients (>19 yrs) who were selected if they had a peripheral blood allogeneic HCT from 2013-2018 and received PTCy for GVHD prophylaxis using a publicly available dataset from the Center for International Blood and Marrow Transplantation Research Program. Kaplan-Meier curves estimated 2-year OS, and differences were compared using log-rank tests. X2 tests helped identify potential confounders. Analyses were stratified by donor type and self-reported race/ethnicity. The Cox Proportional Hazards model evaluated 2-year OS using a backwards elimination method to build the final prediction model. P<0.05 was considered statistically significant. Results Of 4,031 patients included, 70% were NHW, 16% were NHB, and 13% were Hispanic. The most common donor was Haploidentical (Haplo; 64%), followed by matched unrelated donor (MUD; 19%), matched related donor (MRD; 10%), and mismatched unrelated donor 7%). Hispanic patients were younger than NHW and NHB (P<0.0001) and more were transplanted in CR (P<0.0001). Additionally, most Hispanic and NHB patients received a Haplo HCT (77 and 83%, respectively). NHW patients also received Haplo HCTs (57%) as well as MUD HCTs (24%). Most patients had acute myeloid leukemia (40%) followed by myelodysplastic syndrome (22%) and received reduced intensity conditioning (58%). MUD patients who received PTCy had the highest 2-year OS compared to other donors (65 vs 58-61%; P=0.03). Higher OS was observed in younger patients (20-39 yrs: 69% vs 60+ yrs: 53%; P<0.001) and patients with non-malignant diseases (80%) or Hodgkin lymphoma (79%) compared to patients with plasma cell (52%) and myelodysplastic disorders (55%; P<0.0001). For NHW patients, patients transplanted with a MUD had higher OS than other donor types (67 vs 58-60%; p=0.0006). In contrast, NHB transplanted with MRD, Haplo, or MMUD had the highest OS compared to MUD, although this was not statistically significant (61-66% vs 42%; p=0.4). Hispanic patients transplanted with a related donor (MRD and Haplo) had higher OS compared to patients who had an unrelated donor (MUD and MMUD; 66-67 vs 48-58%; P=0.1). Within each donor source, we tested for a racial disparity in OS. There was no difference in OS by race/ethnicity in MRD or MMUD HCTs. In Haplo HCTs, Hispanic patients had the highest OS followed by NHB and then NHW (66, 61, vs 58%; P=0.005). In MUD HCTs, NHW patients had higher OS than Hispanic or NHB patients (67, 48, vs 42%; P=0.02). Significant factors associated with OS in multivariable analyses included donor type, age, disease, year of transplant, conditioning intensity, Karnofsky Performance Score, donor/recipient CMV serostatus, and disease risk index. Results were stratified by race/ethnicity. For NHW patients, mortality risk was higher for HCT patients receiving a MRD, Haplo, or MMUD compared to a MUD (HR=1.25-1.39; P=0.001). In contrast, NHB patients receiving a MUD had a higher risk of mortality compared to a Haplo, MRD, or MMUD (HR=1.67; P=0.06). In Hispanic patients, MUDs and MMUDs had a higher mortality risk than MRD or Haplo HCT (HR=1.48; P=0.07). Conclusion OS differed by race/ethnicity and donor type. Our findings should be validated by expanding the analysis to include patients treated with PTCy after the publication of BMT CTN 1703 results (Bolaños-Mead et al. NEJM. 2023). When selecting donors for HCT patients, consideration should be given to patient race/ethnicity.