Searching for unrelated donor hematopoietic stem cells: availability and speed of umbilical cord blood versus bone marrow.

Unrelated donor (URD) umbilical cord blood (UCB) has several potential advantages over URD BM for hematopoietic stem cell transplantation. To examine the efficiency of donor identification for each of these URD stem cell sources, we reviewed the search processes for all pediatric and adult URD transplantation referrals to the University of Minnesota during a period of 1 year. Of 171 consecutive referrals for URD transplantation, 108 patients proceeded to a formal URD search with selection of at least 1 donor. Significantly more formal UCB searches(54%) than BM searches (21%) were performed for patients who required urgent transplantation (P < .01). At least one 4-6/6 HLA-antigen matched UCB graft but no suitable BM graft was identified for 21 of the 108 patients (19%). The median time required to obtain a URD BM donor (from formal search to clearance of a BM donor) was 49 days (range, 32-293 days) compared to a UCB search time (from formal search to a donor unit chosen) of only 13.5 days (range, 2-387 days). For patients undergoing both BM and UCB searches, 29 more days (95% confidence interval, 21-37 days) were required to identify and clear a URD BM donor than a UCB donor (P < .01). For the 76 patients who proceeded to transplantation, patients receiving UCB received a transplant a median of 25 days more rapidly than did those receiving BM (P < .01). These data confirm that the availability of banked cryopreserved URD UCB grafts allows transplantations for patients with no available BM donor and that URD UCB grafts areavailable considerably faster than are URD BM grafts. Faster availability is a particular advantage for patients requiring urgent transplantation. These unique features of UCB transplantation must be considered in comparisons of the outcomes of UCB versus BM transplant recipients and in the design of prospective trials comparing URD sources.