Allogeneic hematopoietic stem cell transplantation for hematological malignancies: an algorithm for donor selection

Allogeneic hematopoietic stem cell transplantation is a potentially curative treatment for patients with hematological malignancies with donor selection being one of the most important decisions for its success. Several possible donor options have been available, including matched related donor (MRD), matched unrelated donor (MUD), mismatched unrelated donor (MMUD), umbilical cord blood (UCB), and HLA-haploidentical donor. A MRD remains the preferred donor option for optimal transplant outcomes with approximately 30% of the patients having such a donor. Therefore, the remaining 70% of patients require an alternative donor source. Although a MUD is considered to be the next preferred donor option following a MRD, searching for a MUD may delay transplantation for patients unlikely to have a MUD. UCB or HLA-haploidentical donors allow for shorter time to transplant but are associated with increased risk. Recently, T-cell-replete haploidentical transplantation using posttransplantation cyclophosphamide (PTCY) has been developed. This strategy dramatically reduces the risk of graft versus host disease (GVHD), while transplant outcomes after PTCY-based HLA-haploidentical stem cell transplantation seem to be equivalent to those after HLA-matched stem cell transplantation. Recent advances in GVHD prophylaxis may change the algorithm for donor selection.