Evaluation of Cord Blood (CB) TNC & CD34+ Cell Content, Cell Dose & Donor-Recipient 8-Allele HLA-Match By Patient Ancestry: An Analysis of 544 Units in a Racially & Ethnically Diverse Patient Population

Abstract

Introduction Optimal CB unit selection incorporates TNC & CD34+ cell dose & 8-allele donor-recipient HLA-match. How graft characteristics for these parameters vary by patient (pt) race/ ethnicity, however, is unknown. Methods We analyzed cryopreserved TNC & CD34+ cell content, the cell dose incorporating pt weight, & HLA-match of infused & backup (reserved but not shipped) units by pt ancestry in CB transplant (CBT) recipients transplanted 7/2013-6/2018. Units were chosen based on banking practices, TNC & CD34+ dose & 4-6/6 & 8-allele HLA-match. Patient (pt) racial/ ethnic origins were prospectively obtained & grouped per Barker J. et al, BBMT 2010. Results The characteristics of 544 units chosen for 144 diverse CBT recipients by pt ancestry are shown (Table 1). 286 units were infused (142 doubles, 2 singles) & pts had a total of 258 backup units (0-2/pt). The median TNC content of units for Europeans was higher than for Non-Europeans (216 vs 197, p = 0.002). Units for NW Europeans had the highest median TNC content with lowest in units for Africans & White Hispanics. Units chosen for Europeans also had a higher median CD34+ cell content than Non-Europeans (160 vs 132, p = 0.007). Units for NW Europeans had the highest & units for Africans the lowest median CD34+ content. Median TNC/kg was similar in units for European & Non-European pts (2.7 vs 2.5, p = 0.11) & differences between groups were not marked. However, there was a trend for units for Europeans having a higher median CD34+ dose than units for Non-Europeans (1.9 vs 1.7, p = 0.057) with disparity between groups. Although the median 8 allele HLA-match was 5/8 for units chosen for both European & Non-European pts, units identified for non-Europeans were more mismatched (p = 0.017). When the 286 transplanted units (considered the best) were analyzed, the median TNC & CD34+ contents of units were higher for Europeans than non-Europeans (232 vs 216, p = 0.022, & 181 vs 152, p = 0.009). As shown in Table 2, while there were no overall differences in the median TNC & CD34+ doses of units for Europeans & non-Europeans, differences in cell content combined with differences in weights resulted in TNC & CD34+ dose disparities within ancestry groups. For example, NW Europeans (high weight, high CD34+ content) had the highest CD34+ doses; lower content in Asian pts was partially compensated for by low weight; African pts (high weight, low content) had the lowest doses. Finally, there was marked differences in HLA-match distribution by ancestry group: eg only 23% of units for NW Europeans were 3-4/8 vs 40% for S. Europeans, 46% for white Hispanics & 51% for Africans. Conclusions CB extends transplant access to minorities but differences in cellular content translates to many ancestry groups pts having access to only lower dosed units. There are also marked racial/ ethnic disparities in HLA-match. This data supports continued funding of banks to further increase the CB inventory.