Racial Disparity in Myeloablative Hematopoietic Cell Transplantation Outcomes in Patients with Hematological Malignancies Older Than 45 Years.

Introduction: The impact of race on outcomes of allogeneic hematopoietic cell transplants (HCT) has long been a field of research. The Center for International Blood and Marrow Transplant Research (CIBMTR) studies have shown worse survival for Black and Hispanic patients within the first year after HCT, but rates evened out for one-year survivors. From our personal experience, we hypothesize that the outcomes of South Asians (age ≥ 45 years) receiving myeloablative conditioning (MAC) are also worse compared to other races.

Methods: This is a retrospective single-centre study. All patients (age ≥ 45 years) undergoing MAC-HCT for hematological malignancies from 2011-2022 were included. The primary outcome was overall survival (OS). Secondary outcomes were non-relapse mortality (NRM), incidence of grade 2-4 acute graft versus host disease (GVHD), moderate-severe chronic GVHD and relapse incidence (RI). The survival analysis was performed using Kaplan-Meier analysis and log-rank test. The GVHD, NRM and RI rates were calculated using the cumulative incidence (CI) of competing events and the Gray test. EZR was used for statistical analysis.

Results: Of the 483 patients included, there were 28 (5.8%) South Asians (SA), 73 (15.1%), other Asians (East Asians (EA)/Southeast Asians (SEA), and 382 (79.1%) Whites (W). Asians were less likely to get matched unrelated donor-HCT than Whites (SA 21%, EA/SEA 30%, W 45%, p=0.009). The three groups were comparable regarding the recipient and donor sex and performance status. The proportion of SA with HCT-CI ≥ 3 was significantly higher (SA 50%, EA/SEA 37%, W 31%, p=0.03). SA patients were more likely to be obese (body mass index ≥ 30 kg/m²) (SA 29%, EA/SEA 5%, W 19%, p=0.005). There were fewer cytomegalovirus (CMV) serological mismatches among the Asians (SA 25%, EA/SEA 26%, W 43%, p=0.009). There was no difference in the conditioning type and CD34 cell dose. However, fewer Asians received Antithymocyte globulin/post-transplant cyclophosphamide as GVHD prophylaxis (SA 39%, EA/SEA 42%, W 45%, p=0.0009). The median OS was significantly shorter in SA (SA 19, EA/SEA 103, W 65 months, p=0.04). The 2-year NRM was significantly higher in SA (SA 35.7%, EA/SEA 13.7%, W 16%, p=0.03). The CI of grade 2-4 acute and moderate-severe chronic GVHD was not significantly different (p=0.7 & 0.6). The 2-year RI was also not significantly different (SA 28.5%, EA/SEA 24.7%, W 28%, p=0.8).

Conclusion: Our study confirms that South Asians aged ≥ 45 years have worse survival after MAC-HCT. Supportive care is unable to overcome the differences in the outcomes.