The impacts of total body irradiation on umbilical cord blood hematopoietic stem cell transplantation

Background: Umbilical cord blood hematopoietic stem cells are commonly used for hematopoietic system reconstitution in recipients after umbilical cord blood transplantation (UCBT). However, the optimal conditioning regimen for UCBT remains a topic of debate. The exact impact of total body irradiation (TBI) as a part of conditioning regimens remains unknown. Objectives: The aim of this study was to evaluate the impacts of TBI on UCBT outcomes. Design: This was a multi-institution retrospective study. Methods: A retrospective analysis was conducted on the outcomes of 136 patients receiving UCBT. Sixty-nine patients received myeloablative conditioning (MAC), in which 33 underwent TBI and 36 did not, and 67 patients received reduced-intensity conditioning (RIC), in which 43 underwent TBI and 24 did not. Univariate and multivariate analyses were conducted to compare the outcomes and the post-transplant complications between patients who did and did not undergo TBI in the MAC subgroup and RIC subgroup, respectively. Results: In the RIC subgroup, patients who underwent TBI had superior overall survival (adjusted hazard ratio [aHR] = 0.25, 95% confidence interval [CI]: 0.09–0.66, p = 0.005) and progression-free survival (aHR = 0.26, 95% CI: 0.10–0.66, p = 0.005). However, in the MAC subgroup, there were no statistically significant differences between those receiving and not receiving TBI. Conclusion: In the setting of RIC in UCBT, TBI utilization can improve overall survival and progression-free survival. However, TBI does not show superiority in the MAC setting.