Application Timing-Dependent Impact of Donor Source on Outcomes After Allogeneic Hematopoietic Stem Cell Transplantation for Adult T-Cell Leukemia/Lymphoma.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is usually performed as a curative treatment for adult T-cell leukemia/lymphoma (ATL), following first-line chemotherapy. We conducted a nationwide retrospective study to examine the prognostic impact of donor sources based on transplantation application timings: human leukocyte antigen (HLA)-matched related donor (MRD; n = 253), unrelated donor (URD; n = 656), unrelated cord blood (U-CB; n = 599), and HLA-haploidentical related donor with post-transplant cyclophosphamide (PT-CY; n = 166). In patients with the early application of allo-HSCT (< 100 days from diagnosis), the multivariate analysis showed no significant difference in overall mortality (OM) among all donor sources. Regarding the middle timing of allo-HSCT (100-179 days), the U-CB group showed higher OM than the MRD group (hazard ratio [HR], 1.37; p = 0.013), while the URD and PT-CY groups showed no significant difference in OM with the MRD group. Concerning the late timing of allo-HSCT (180-270 days), the U-CB (HR, 1.88; p = 0.005) and PT-CY groups (HR, 1.90; p = 0.043) showed higher OM than the MRD group, whereas the URD group exhibited comparable OM to the MRD group. The present study demonstrated the differential impact of the graft source based on the timing of allo-HSCT for ATL; therefore, it is important to select an optimal alternative donor based on application timing.