On Dec. 8, 2025, a study led by Roswell Park Comprehensive Cancer Center reveals that a patient’s race and ethnicity, as well as how closely matched they are to their stem cell donor, can all significantly affect clinical outcomes for those who undergo stem cell transplant as treatment for cancer — despite the introduction of a new standard-of-care drug regimen shown to lower the risk of graft-versus-host disease, a potentially fatal side effect. Study results are expected to lay the groundwork for improved selection of stem cell donors.

The findings relate to allogeneic hematopoietic stem cell transplant (HCT), in which patients receive stem cells drawn from a consenting donor’s blood as part of their treatment for some cancers, including many forms of leukemia and lymphoma.

“The biggest takeaway of our analysis is that for patients undergoing allogeneic stem cell transplant, the patient’s race, ethnicity and age should be a strong consideration in identifying their stem cell donor,” explains first and presenting author Megan Herr, PhD.

The research marks the first evaluation of race- and ethnicity-related disparities in overall survival since the standard of care changed to include administration of the chemotherapy drug cyclophosphamide (PTCy) after an allogeneic transplant, which involves donor-provided stem cells. In the pre-PTCy era, Hispanic and non-Hispanic Black HCT patients had higher mortality rates than non-Hispanic white patients and were less likely to use an unrelated stem cell donor.

Cyclophosphamide has dramatically reduced the risk of graft-versus-host disease (GVHD) — which occurs when donor cells attack the patient’s body. Research led nationally by study co-author Shernan Holtan, MD, Chief of Blood and Marrow Transplantation at Roswell Park, paved the way for expanded use of cyclophosphamide, a shift that also made stem cell transplants increasingly available to minority patients.

But this latest study shows that disparities in overall survival persist between racial and ethnic groups, and donor type plays a key role. Analyzing data from the Center for International Blood and Marrow Transplant Research (CIBMTR) for more than 4,000 patients who received cyclophosphamide after undergoing allogeneic transplant between 2013 and 2018, investigators looked at three main racial/ethnic groups — Hispanic, non-Hispanic Black and non-Hispanic white — and compared overall survival rates.

They also factored in the type of transplant according to donor type: haploidentical — a “half-matched” donor, typically a family member — or a matched unrelated donor (MUD), matched related donor (MRD) or mismatched unrelated donor (MMUD).