Racial/ ethnic disparities in availability of volunteer unrelated donors for allogeneic transplantation.

Despite the global unrelated donor (URD) registry size, the degree to which URD availability is a transplant barrier is not established. We evaluated the availability of 3,843 URDs requested for 455 diverse adult patients (predominantly with acute leukemia). URDs for non-Europeans were more likely to be domestic and had markedly lower Donor Readiness Scores. Of URDs requested for confirmatory HLA-typing (CT) alone (i.e. without simultaneous workup), 1,894/3,529 (54%) were available. Availability of domestic URDs was 45%. Donor Readiness Score was highly predictive of CT availability. Compared with Europeans (n=335), more non-European patients (n=120) had >10 URDs requested and <5 available. Of workup requests (after CT or CT-workup), <70% (604/889, 68%) were available. More non-Europeans had <2 URDs available. URD availability for CT was markedly worse for non-Europeans, with availabilities for African, non-Black Hispanic, and Asian patients of 150/458 (33%), 120/258 (47%) and 119/270 (44%), respectively, with further decrements in URD workup availability. Our data suggest the functional size of the URD pool is much smaller than appreciated, mandating major operational changes for transplant Centers and donor registries. Likelihood of donor availability should have a high priority in donor selection. Considering patient ancestry and URD Donor Readiness Scores, Centers should pursue, and registries permit, simultaneous pursuit of many URDs, and abandon futile searches. Patients should be informed about their likelihood of donor availability and alternative options. Finally, while registries should address high URD attrition and speed procurement, use of all HLA-disparate graft types is needed to facilitate timely transplantation for all.

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

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.

Availability of cord blood extends allogeneic hematopoietic stem cell transplant access to racial and ethnic minorities.

Allogeneic transplant access can be severely limited for patients of racial and ethnic minorities without suitable sibling donors. Whether cord blood (CB) transplantation can extend transplant access because of the reduced stringency of required HLA-match is not proven. We prospectively evaluated availability of unrelated donors (URD) and CB according to patient ancestry in 553 patients without suitable sibling donors. URDs had priority if adequate donors were available. Otherwise ≥4/6 HLA-matched CB grafts were chosen utilizing double units to augment graft dose. Patients had highly diverse ancestries including 35% non-Europeans. In 525 patients undergoing combined searches, 10/10 HLA-matched URDs were identified in 53% of those with European ancestry, but only 21% of patients with non-European origins (P < .001). However, the majority of both groups had 5-6/6 CB units. The 269 URD transplant recipients were predominantly European, with non-European patients accounting for only 23%. By contrast, 56% of CB transplant recipients had non-European ancestries (P < .001). Of 26 patients without any suitable stem cell source, 73% had non-European ancestries (P < .001). Their median weight was significantly higher than CB transplant recipients (P <.001), partially accounting for their lack of a CB graft. Availability of CB significantly extends allo-transplant access, especially in non-European patients, and has the greatest potential to provide a suitable stem cell source regardless of race or ethnicity. Minority patients in need of allografts, but without suitable matched sibling donors, should be referred for combined URD and CB searches to optimize transplant access.