RESUMEN
In single unrelated cord blood transplantation (UCBT), an increasing number of HLA allele mismatches (MM) has been associated with inferior overall survival (OS) and attributed to higher transplant-related mortality (TRM). Previous studies on the role of allele-level HLA matching after double UCBT (dUCBT) showed conflicting results. In this study, we report the impact of allele-level HLA matching on the outcomes of a large dUCBT cohort. We included 963 adults with hematologic malignancies, with available allele-level HLA matching at HLA-A, -B, -C, and -DRB1, receiving dUCBT between 2006 to 2019. Assignment of donor-recipient HLA match was performed considering the unit with the highest disparity with the recipient. Three hundred ninety-two patients received dUCBT with 0 to 3 MM and 571 with ≥4 allele MM. For recipients of dUCBT with 0 to 3 MM, day-100 and 4-year TRM were 10% and 23%, respectively, compared with 16% and 36% for those with ≥4 MM. A higher degree of allele MM was also associated with the worse neutrophil recovery and lower incidence of relapse; no significant effect on graft-versus-host disease was observed. Patients receiving units with 0 to 3 MM had a 4-year OS of 54% compared with 43% for those receiving units with ≥4 MM. The inferior OS associated with higher HLA disparity was only partially mitigated by increased total nucleated cell doses. Our results confirm that allele-level HLA typing is a significant factor for OS after dUCBT, and units with ≥4 MM (≤4/8 HLA-matched) should be avoided if possible.