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Umbilical Cord Blood (UCB) transplantation: an alternative to the use of unrelated volunteer donors?

Cryopreserved umbilical cord blood (UCB) from 4-6/6 HLA-A,B antigen and DRB1 allele matched unrelated neonatal donors contains sufficient numbers of hematopoietic stem cells (HSC) to engraft most younger pediatric patients with leukemia. Recent data demonstrate promising results in larger children and adults, as well as in patients with nonmalignant disorders. As a result, the number of UCB transplantations (UCBT) being performed is increasing dramatically. UCB has the clear benefits of rapid availability and a reduced stringency of requirement for HLA match. The latter attribute has the potential to extend the donor pool, which is of great importance for racial and ethnic minorities. Furthermore, new preparative regimens combined with double-unit grafts have been associated with improved engraftment and survival in larger children and adults, making UCBT a viable potential alternative to unrelated volunteer donor transplantation, especially in preference to transplantation using mismatched volunteers. This review summarizes the current status of unrelated donor UCBT and describes both the challenges and current areas of research associated with this HSC source.