Hematopoietic stem-cell transplantation (HSCT) is a potentially lifesaving therapy
for several blood cancers and other diseases. For patients without a suitable related
HLA-matched donor, unrelated-donor registries of adult volunteers and banked umbilical
cord-blood units, such as the Be the Match Registry operated by the National Marrow
Donor Program (NMDP), provide potential sources of donors. Our goal in the present
study was to measure the likelihood of finding a suitable donor in the U.S. registry.
Using human HLA data from the NMDP donor and cord-blood-unit registry, we built population-based
genetic models for 21 U.S. racial and ethnic groups to predict the likelihood of identifying
a suitable donor (either an adult donor or a cord-blood unit) for patients in each
group. The models incorporated the degree of HLA matching, adult-donor availability
(i.e., ability to donate), and cord-blood-unit cell dose.
Our models indicated that most candidates for HSCT will have a suitable (HLA-matched
or minimally mismatched) adult donor. However, many patients will not have an optimal
adult donor--that is, a donor who is matched at high resolution at HLA-A, HLA-B, HLA-C,
and HLA-DRB1. The likelihood of finding an optimal donor varies among racial and ethnic
groups, with the highest probability among whites of European descent, at 75%, and
the lowest probability among blacks of South or Central American descent, at 16%.
Likelihoods for other groups are intermediate. Few patients will have an optimal cord-blood
unit--that is, one matched at the antigen level at HLA-A and HLA-B and matched at
high resolution at HLA-DRB1. However, cord-blood units mismatched at one or two HLA
loci are available for almost all patients younger than 20 years of age and for more
than 80% of patients 20 years of age or older, regardless of racial and ethnic background.
Most patients likely to benefit from HSCT will have a donor. Public investment in
donor recruitment and cord-blood banks has expanded access to HSCT. (Funded by the
Office of Naval Research, Department of the Navy, and the Health Resources and Services
Administration, Department of Health and Human Services.).