‘Tremendous racial and ethnic disparity’ observed in access to matched donor stem cells
Patients with cancer who need a bone marrow transplant are less likely to find a suitable match if they are of southern-European or non-European descent, according to results of a prospective study published in Blood Advances.
Among all ethnicities, patients of African descent are the least likely to receive a transplant from a fully matched donor.
“We have identified tremendous racial and ethnic disparity in transplant access,” Juliet N. Barker, MBBS, director of the cord blood transplant program at Memorial Sloan Kettering Cancer Center, said in a press release. “What’s more, it has been thought by some that if you just increase the number of registered adult donors that it would resolve this problem, but it hasn’t. This study provides a clear demonstration of how important it is to fund initiatives that will improve outcomes of alternative donor transplantation, including the use of unrelated donor cord blood.”
Barker and colleagues analyzed 1,312 patients (median age, 51 years; range, < 1-70) with life-threatening blood cancers who began donor searches between 2005 and 2017 at Memorial Sloan Kettering Cancer Center.
Cancer diagnoses included acute leukemia (n = 696), myelodysplasia or myeloproliferative disorders (n = 207), lymphomas (n = 390) and aplastic anemia (n = 19).
Patient ethnicities included northwestern European (n = 256), Eastern European (n = 214), southern European (n = 133), mixed European (n = 263), Asian (n = 95), African (n = 145), white Hispanic (n = 97), Middle Eastern (n = 30), and mixed non-European (n = 79).
More than half of all patients (55%) received transplants from 8/8 HLA-allele matched unrelated donors, whereas 17% received transplants from 7/8 HLA-allele matched unrelated donors, 24% underwent cord blood transplants and 4% received none of these.
Results showed that patients of European descent were more likely to receive an 8/8 HLA-matched unrelated donor transplant than non-Europeans (67% vs. 33%; P < .001) and much less likely to have no 7/8 or 8/8 unrelated donor transplant or cord blood graft (1% vs. 9%; P < .001).
Southern Europeans received these transplants at a rate of 41%, which was similar to that of Asians (34%) as well as white Hispanics (35%). Africans appeared least likely (18%) to receive an 8/8 transplant.
Overall, the distribution of 8/8 unrelated donor transplants favored northwestern Europeans (27%), mixed Europeans (23%) and Eastern Europeans (21%) over southern Europeans (8%), non-European mixes (6%), white Hispanics (5%), Asians (4%), Africans (4%) and Middle Easterners (2%).
The 7/8 unrelated donor transplant recipients included mixed Europeans (21%), northwest Europeans (16%), Africans (15%), southern Europeans (12%), eastern Europeans (12%), white Hispanics (10%), Asians (7%), mixed non-Europeans (5%), and Middle Easterners (2%).
Researchers noted the availability of cord blood extended transplant access, as the majority of
cord blood transplant recipients (54%) were non-European.
Most of the 51 patients who did not receive a 7/8 or 8/8 unrelated donor transplant or a cord blood graft were non-European (80%) and of African descent (57%).
In analyzing donor access by time period, researchers found the marked racial disparity in access to 8/8 unrelated donor transplants persisted in recent years. Among 78 recent African patients, 46% underwent cord blood transplant and 14% did not have a 7/8 or 8/8 unrelated donor transplant or a cord blood graft.
Unrelated donor searches have improved and, as a result, are likely to be abandoned quicker in patients who are unlikely to have an 8/8 unrelated donor match, which serves as a limitation to this study. Researchers also were limited by an inability to address ancestry distribution for haploidentical donor transplant recipients.
“It has been previously recognized that non-European patients have difficulties finding a match, but we have also found that those originating from the [southern region of Europe] can also be difficult to match,” Barker said. “It is also important to fully understand the patient’s ancestry, as it cannot be assumed that a patient who is predominately European, but may have part non-European origins, is going to have a match.” – by John DeRosier
Disclosures: Barker reports research funding from Angiocrine Bioscience and an unrestricted educational grant from Gamida Cell. Please see the study for all other authors’ relevant financial disclosures.