Abstract B121: HLA-mismatched unrelated donor hematopoietic cell transplantation with post-transplant cyclophosphamide improves clinical outcomes for racial and ethnic minority patients with hematologic malignancies

Abstract

Abstract Introduction: Racial and ethnic disparities exist in three areas related to hematopoietic cell transplantation (HCT): donor availability, access, and post-HCT outcomes. A significant barrier to access to HCT for patients (pts) of racial or ethnic minorities (REM) is the limited availability of fully matched donors (i.e., grafts matched at HLA-A, -B, -C, and -DRB1 loci) in volunteer registries. While mismatched unrelated donor (MMUD) grafts (i.e., <7/8 match) can be offered to pts without matched donors, MMUD HCT results in poor survival when traditional graft-versus-host disease (GVHD) prophylaxis (PPx) is used. GVHD PPx with post-transplantation cyclophosphamide (PTCy) is associated with favorable survival after haploidentical HCT, and promising outcomes have been reported in a prospective multicenter study utilizing PTCy in MMUD HCT. Herein, we analyzed the outcomes of an ethnically diverse cohort of pts who underwent MMUD HCT with PTCy at two large urban transplant centers. Objectives and Methods: Subjects receiving HCT from an MMUD from 2010-to 2020 at the University of Miami and Memorial Sloan-KetteringCancer Center were included. Pts were stratified by age, HCT indication, race/ethnicity, graft type, conditioning intensity, disease status, and degree of HLA mismatch. The primary study endpoint was one-year overall survival (OS). Secondary endpoints were event-free survival (EFS), non-relapse mortality (NRM), and cumulative incidence of acute and chronic GVHD. Results: A total of 82 pts were evaluated. The median age at HCT was 60 years (21-75), the most common indication for HCT was acute leukemia (51%), 41% of pts received an ablative conditioning regimen, and 50% received peripheral blood (PB) grafts. Forty-four percent identified as non-Hispanic white (NHW), and 56% identified as REM (Non-Hispanic Black: 30%; Hispanic: 64%; Asian/Pacific: 4.3%). The two groups (NHW vs. REM) were well-matched for leading HCT indication, disease-risk index, degree of mismatch, and disease status at HCT. REM pts were younger (median age at HCT 65 vs 56 years for NHW, p=0.001) and more likely to receive a PB graft (63% vs 40%, P = 0.04). One-year OS was 75%, EFS was 69%, and NRM was 16% for the entire cohort. Grade 3-4 acute GVHD at day 180 post-HCT was 15%, and one-year severe chronic GVHD was 9%. OS was comparable between 7/8-matched and highly-mismatched (<6/8) HCT recipients (75% vs. 76%, respectively; P >0.9). There were no differences in one-year OS (77% vs 74%, p = 0.9) and EFS (63% vs 72%, p = >0.9) between NHW and REM pts. Similarly, rates of acute (17% vs 13%, p = 0.5) and chronic GVHD (5.7% vs 11%, p = 0.5) were comparable between NHW and REM pts. Conclusion: PTCy resulted in encouraging clinical outcomes following MMUD HCT. Post-HCT OS, RFS, and GVHD rates were comparable between NHW and REM pts and those receiving 7/8 or highly mismatched grafts. Favorable post-HCT outcomes following MMUD with PTCy may increase HCT utilization and access for REM pts. Citation Format: Antonio M. Jimenez Jimenez, Sunil Iyer, Krishna Komanduri, Samantha Brown, Trent Wang, Stephanie Chinapen, Denise Pereira, Sean Devlin, Mark Goodman, Amer Beitinjaneh, Craig Sauter, Lazaros Lekakis, Miguel Angel Perales, Doris Ponce, Brian Shaffer. HLA-mismatched unrelated donor hematopoietic cell transplantation with post-transplant cyclophosphamide improves clinical outcomes for racial and ethnic minority patients with hematologic malignancies [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr B121.