Unrelated cord blood transplantation vs. related transplantation with HLA 1-antigen mismatch in the GVH direction.

The donor selection superiority of HLA 1-antigen mismatched related donor versus unrelated cord blood (UCB) is an important issue for patients without an HLA-matched related or unrelated donor. Using Japanese registry data, we analyzed patients with leukemia and myelodysplastic syndrome who received transplantation using UCB or from a related donor with 1-antigen mismatch in the graft-versus-host (GVH) direction (RD/1AG-MM-GVH). Compared to the UCB group, neutrophil engraftment was significantly faster, and the incidences of acute and chronic GVHD were significantly higher in the RD/1AG-MM-GVH group. As a result, there was no significant difference in overall survival between transplantation using the RD/1AG-MM-GVH and UCB. However, the HLA-B-antigen mismatched group showed significantly inferior overall survival. The RD/1AG-MM-GVH group using anti-thymocyte globulin (ATG) showed neutrophil engraftment comparable to that of the non-ATG group and a GVHD incidence similar to that of the UCB group, which resulted in a better overall survival rate in the ATG than in the UCB group. In particular, the adverse effects of HLA-B mismatch were not observed in the ATG group. RD/1AGMM-GVH transplantation using ATG could potentially improve outcomes, and a prospective study of RD/1AGMM-GVH transplantation using low-dose ATG is currently ongoing.