Prospective Evaluation of Unrelated Donor Cord Blood and Haploidentical Donor Access Reveals Graft Availability Varies by Patient Ancestry: Practical Implications for Donor Selection

Abstract

The availability of cord blood (CB) and haploidentical (haplo) donors in all patient populations is not established. We have investigated the addition of haplo-CD34⁺ cells to CB grafts (haplo-CBT) to speed myeloid engraftment. Thus, we have prospectively assessed CB and haplo donor availability in adult patients without 8/8 HLA-allele matched unrelated donors (URDs). Analysis of 89 patients eligible for haplo-CBT revealed 4 distinct patient groups. First, 6 patients (7% of total, 33% non-European) underwent CBT only as they had no suitable family members to type. In group 2, 49 patients (45% non-European) received haplo-CBT using the first haplo donor chosen. Group 3 (n = 21, 76% non-European) underwent CBT with/without haplo. In this group, the first haplo donor chosen failed clearance in 20 patients and transplantation was too urgent to permit donor evaluation in 1. Fifty-three haplo donors were evaluated (2 to 6 per patient) for 21 group 3 patients, and 43 of 53 (81%) haplos failed clearance for predominantly medical and/or psychosocial reasons. Group 4, (n = 13, 85% non-European with a high median weight of 96 kilograms) had no CB grafts with/without no haplo donors. Overall, African patients had the worst donor availability with only 65% having a suitable CB graft and only 44% having a suitable haplo donor. Additionally, in non-European patients, a greater number of haplos required evaluation/patient to secure a suitable haplo graft. Although these data should be confirmed in a larger study, it suggests that there are barriers to the availability of both CB and haplo grafts in adult patients without 8/8 URDs, especially in those with African ancestry, and has multiple practical implications for patient management.

Keywords: Cord blood transplantation; Haploidentical donors; Unrelated donors.

Figure 1.. Distribution of CB and haplo donor availability in 89 patients evaluated for combined haplo-CBT.

Patients were divided into whether they had CB but no haplo-identical donors (Group 1), CB and haplo-identical donors with the first haplo-donor evaluated clearing for donation (Group 2), CB grafts with or without (+/−) haplo donors with multiple haplo donors evaluated per patient (Group 3), and no CB grafts with or without (+/−) no haplo grafts (Group 4).