Umbilical cord blood: The promise and the uncertainty.

Unfortunately, many patients referred for hematopoietic cell transplant will not have a fully matched related donor, and finding matched unrelated donors through the registry may be difficult, especially if the recipient is not of Northern European descent [N Engl J Med 2014;371:339-348]. Umbilical cord blood (UCB) has been an available graft source for hematopoietic cell transplant for more than 30 years, since the first UCB transplant was performed in the late 1980s [N Engl J Med 1989;321:1174-1178]. UCB is readily available, has low immunogenicity, and does not require as strict of human leukocyte antigen (HLA) matching compared to other graft sources [N Engl J Med 2004;351:2265-2275]. According to data from the Center for International Blood and Marrow Transplant Research (CIBMTR), an estimated 500 patients in the US will have received a UCB transplant in 2018. Since 2014, haploidentical transplants have surpassed UCB transplants performed in the United States (CIBMTR Summary Slides, 2018, available at https://www.cibmtr.org). Increased use of haploidentical transplants has brought to light concerns about UCB transplants, including delayed engraftment and graft failure, increased nonrelapse mortality, increased infection risk, and UCB acquisition costs [Lancet Oncol 2010;11:653-660; Biol Blood Marrow Transplant 2019;1456-1464]. These concerns will need to be addressed for UCB to remain a viable option as a graft source for hematopoietic cell transplant. Other promising therapeutic benefits for UCB, in addition to hematopoietic cell transplant, is its use in regenerative medicine and immune modulation, which is currently being evaluated in ongoing clinical trials.