When looking for appropriate stem cell/bone marrow donors, clinicians tend to stay away from older donors with clonal hematopoiesis — a condition common with aging in which mutations associated with blood cancers are found in the blood of healthy people — because of concerns about passing potentially premalignant stem cells to the recipient.

However, a new study, co-authored by researchers at the Johns Hopkins Kimmel Cancer Center and Dana-Farber Cancer Institute in Boston, found an interesting curve: In some patients who have received a stem cell transplant, donor cells with CH can improve overall and disease-free survival and reduce the risk of relapse.

A report on the research, published in November in the Journal of Clinical Oncology, provides scientific evidence that individuals aged 40 or older with clonal hematopoiesis should not necessarily be excluded from stem cell donation. Since matched related siblings are often considered the best available options for patients undergoing stem cell transplantation, the presence of CH, particularly in older siblings, should not necessarily be an exclusion criteria for donation, says study co-author Lukasz Gondek, a Johns Hopkins oncologist.

“The paper provides evidence that donors with mutations in DNMT3A, the most commonly affected gene in CH, can be safely used,” he says. “Moreover, in some instances, using the donors with DNMT3A mutations may be beneficial, as mutated donor immune cells may provide a better anti-leukemic effect.” However, other rarer types of CH may produce undesirable outcomes, notes Gondek, who adds that research is ongoing.