Alternative transplant donor sources: Is there any consensus?

Purpose of Review: To review the data supporting the use of alternative donors for hematopoietic cell transplantation of patients with high-risk or advanced hematological malignancies. Recent Findings: Advances in supportive therapy and technology have improved the safety and efficacy of alternative donors for hematopoietic cell transplantation. Molecular techniques have allowed for better human leukocyte antigen matching of unrelated adult donors. Novel strategies such as adoptive regulatory T cells or posttransplantation cyclophosphamide contributed to better outcomes after partially matched related donors. In umbilical cord blood transplantation, the ability to find adequately dosed single-unit grafts, the utilization of double-unit grafts, and novel methodologies such as ex-vivo expansion, intrabone injection, and priming to accelerate engraftment are promising. Available retrospective studies suggest despite the differences in hematopoietic recovery, risk of graft-versus-host disease, and relapse, long-term outcomes are similar between different alternative donor types. Summary: In the absence of a suitable matched related donor, most patients will be able to find an alternative donor to proceed to a potentially curative allogeneic transplantation. Emerging new technologies will further improve the safety and efficacy of alternative donor transplantation. Ongoing and future randomized studies will better define the relative efficacy of alternative donor types.