Variations in the Use of a Race/Ethnic Matched Donor or Cord Blood Unit in Allogeneic Transplants

AIM:   The composition and frequency of HLA alleles and haplotypes vary by race/ethnic populations.    Consequently, it is thought that patients (pts) in need of an allogeneic stem cell transplant are most likely to identify a suitably HLA matched cell source within their own racial/ethnic group.  This study evaluated the degree of race/ethnic matching for U.S. pts who received a transplant facilitated by Be The Match Registry® (BTMR). 

METHOD:  11,870 transplants for U.S pts using a U.S donor or cord blood unit (CBU) in BTMR database from January 2008 to October 2013 were evaluated.  Pt cohort was restricted to those who self identified their race/ethnicity under the broad classification of Black (AFA), Asian/Pacific Islander (API), White (CAU), and Hispanic (HIS).  Cell source self identified race/ethnicity were clustered into the broad race group of AFA, API, CAU, and HIS.  If the broad race/ethnicity of the pt and source were identical the case was considered a match.  When more than one race and/or ethnicity was reported in a pt/source they were considered race/ethnic matched if at least one same broad race/ethnic group was reported for both.  9243(78%) of the pts were self described as CAU with 1108 AFA, 917 HIS, and 602 API contributing 9.3%, 7.7%, and 5.1%, respectively.  Comparison of race matching along with HLA matching at transplant was also evaluated.  The HLA match was assigned a match category of x of 10 for donors and x of 6 (antigen level HLA-A,B, allele HLA-DRB1) for CBUs utilizing the typing provided by the transplant center. 

RESULTS:  Figure 1 shows the percent of race/ethnic matching between the pt and transplanted cell source.  Greater than 90% of CAU and HIS pt populations transplanted with a race/ethnic matched donor or CBU, contrasted with AFA and API pts who transplanted with race/ethnic matched CBU less than 60% of the time.    AFA and API pts showed variation between cell sources, transplanting less often with a race/ethnic matched CBU than donor.

Figure 1:

Further analysis of the level of HLA match in relation to race match shows increased HLA mismatches when the source was race/ethnic mismatched (Figure 2).  In all populations, when the source is race/ethnic mismatched with the pt, fewer 10/10 donors and increased 4/6 or worse CBUs were used.  API pts were more often transplanted with an HLA mismatched source when the source is also race/ethnic mismatched.

Figure 2:

CONCLUSION:  This study shows that AFA, API, CAU, and HIS pts, transplanted in the past 5 years, most utilized a race/matched donor.  From 2008 to present, greater than 70% of donors and greater than 50% of CBU transplants were race/ethnic matched between the pt and cell source.  In addition, better HLA matching was observed when the pt and cell source were matched for race/ethnicity.