Outcomes from unrelated donor hematopoietic stem cell transplantation.

BACKGROUND Allogeneic hematopoietic cell transplantation (HCT) offers a curative treatment option for management of a variety of hematologic malignancies. While sibling donors have been the gold standard for adult patients in need of an HCT, not all patients have a suitable family donor. The availability of unrelated volunteer donor registries and alternative stem cell sources has expanded the wide application of this procedure. METHODS PubMed and MEDLINE were searched for human trials and the English language from 2001 to 2011. Factors influencing transplantation outcomes involving unrelated donors over the last decade are discussed, and feasible alternative stem cell sources when a matched unrelated donor is not available are reviewed. RESULTS HCT using a matched unrelated donor offers outcomes comparable to sibling HCT due to current molecular-based HLA typing and improvements in conditioning regimens and/or supportive care. The primary factor that contributes to improved outcome is the degree of donor-to-recipient HLA matching. The selection of younger unrelated donors has also been associated with improved outcomes in HCT. Evidence supports the universal application of matched unrelated donors even in high-risk leukemia and/or older patients. In adult patients without a matched related donor, other promising options as stem cell source includes mismatched unrelated donors, umbilical cord blood units, and haploidentical donors. CONCLUSIONS With current methodologies for molecular HLA typing and supportive care tools, outcomes of transplants with matched unrelated donors are comparable to those achieved with sibling donors. Alternative stem cell donors when a matched unrelated donor is not available are feasible expanding the stem cell donor pool.