Racial Disparities in Matched Volunteer Stem Cell Donors
Although the pool of registered bone marrow donors has increased in recent years, a new study suggests that most patients of southern European and non-European descent are unlikely to have a suitable match if they need a bone marrow transplant. If an immediate registry search does not identify a donor, alternative transplant strategies should be considered, according to a study published by Barker et al in Blood Advances.
The ideal bone marrow donor is usually a brother or sister with the same genetic markers as the recipient. However, for those who do not have a suitable sibling, transplant from a matched unrelated volunteer donor is usually considered the next best option. At the Memorial Sloan Kettering Cancer Center’s Adult Bone Marrow Service—a large and ethnically diverse transplant program where this study was conducted—approximately 75% of patients do not have a sibling match.
Methods and Findings
First study author Juliet Barker, MBBS, Director of the Cord Blood Transplant Program at Memorial Sloan Kettering Cancer Center, and her team followed 1,312 patients who needed a bone marrow transplant for treatment of life-threatening blood cancers and who initiated donor searches from 2005 to 2017. All patients shared their family history as far back as known, including where they were born, what they considered their race and ethnicity to be, and where their parents and grandparents were born. Researchers categorized the patients into groups in terms of their racial and ethnic origins and tracked if they could go to transplant with a matched adult donor, or whether they required a mismatched adult donor or a transplant using neonatal cord blood cells.
Dr. Barker and colleagues reported that people of European descent were more likely to receive a transplant from an unrelated fully matched donor than were non-Europeans. Among all Europeans in the study, 67% received a matched transplant, compared to 33% of non-Europeans (including Asians, White Hispanics, and Africans).
Compared to people from other parts of Europe, the majority of Southern Europeans were unlikely to have a fully matched donor (41% of Southern Europeans vs 64%–77% for other European patients). Southern Europeans’ rate of receiving a match was closer to the rates observed with Asians and White Hispanics. Individuals of African descent were least likely to undergo transplantation from a fully matched donor.
Study Implications
“We have identified tremendous racial and ethnic disparity in transplant access,” said Dr. Barker. “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.”
She added, “It has been previously recognized that non-European patients have difficulties finding a match. But we have also found that those originating from the south of Europe can also be difficult to match. This hasn't always been widely appreciated. It is also important to fully understand the patient’s ancestry as it cannot be assumed that a patient who is predominantly European—but may have part non-European origins—is going to have a match.”
The majority of those who did not have a full match either received a partial match (17% of all patients) or cord blood transplant (24%). Of all patients, 4% did not receive any type of transplant, and the majority of these individuals were of African descent.
“Transplant centers now have the technology to search adult donor registries and immediately estimate the chance their patient will have a matched donor,” said Dr. Barker. “If the search is poor, centers should immediately pursue alternative donors. Futile adult donor searches and donor drives should be abandoned. This is more and more important as our population increasingly becomes more diverse.”
Disclosure: The study authors’ full disclosures can be found at bloodadvances.org.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
