[Allogeneic hematopoietic stem cell transplantation: donor selection in the new era]

Allogeneic hematopoietic stem cell transplantation is a curative treatment for hematological malignancies and bone marrow failure syndromes, but appropriate donor selection is important to reduce the risk of complications such as graft-versus-host disease (GVHD) and poor engraftment. Use of HLA-matched sibling donors has been decreasing, which has led to increased use of unrelated donors, cord blood, and haploidentical donors. In haplo-transplantation, outcomes are influenced by HLA epitope compatibility (which depends on the method of GVHD prophylaxis) and the number of CD34+ cells infused. In cord blood transplantation, the number of CD34+ cells and CFU-GM are important. In unrelated bone marrow transplantation, HLA-DPB1 and HLA epitope level compatibility are also considered important. In the future, comprehensive donor selection that considers not only HLA compatibility but also epitope compatibility and donor characteristics might be required. The use of new evaluation indices such as the PIRCHE score should improve the safety and success rate of transplantation.