• Posted May 28, 2024

Strategy Could Expand Stem Cell Donor Pool for People Battling Blood Cancers

An older drug used in a new way could open the path for more patients with potentially deadly blood cancers to receive a lifesaving stem cell transplant, a new study finds.

The drug, cyclophosphamide, could help patients receive a stem cell transplant even if the donor isn't a relative and only partially matches their blood type, researchers report.

Blood cancer patients had a high survival rate of 79% at one year after receiving a stem cell transplant from a stranger followed up by treatment with cyclophosphamide, researchers found.

“The outcomes seem to be very comparable to those of a fully matched donor,” said researcher Dr. Antonio Jimenez Jimenez, a physician-scientist with the University of Miami Miller School of Medicine.

Administering cyclophosphamide several days after transplantation can help patients avoid graft-versus-host disease (GvHD), a deadly side effect in which the transplant mounts an immune attack on the patient.

GvHD typically occurs in 60% to 80% of transplants in which the donor and recipient aren't related, according to the National Institutes of Health.

But after one year, about half (51%) patients in the new study had not developed GvHD and had not suffered a cancer relapse, results show.

Finding a matched donor is a major hurdle for patients with blood cancer, researchers said.

The National Marrow Donor Program contains more than 40 million potential donors, but there are disparities in the program.

Only half of Hispanic and a quarter of Black patients can find a fully matched donor, compared with more than 70% of white patients, researchers noted.

Cyclophosphamide has been increasingly used over the past decade or so to help patients accept partial donor matches from relatives, researchers said. The chance of a full match from a sibling is only 25%, and the chance of a partial match is 50%.

This caused researchers to wonder if cyclophosphamide might also work for transplants from donors who are partially matched but not related to the patient.

This approach led to high survival rates among 80 patients receiving bone marrow transplants from partially matched but unrelated donors in an earlier study.

But treatment of blood cancer has been focusing more on stem cell transplants, because it's easier to collect stem cells from a donor than bone marrow, researchers noted.

In the new study, researchers tested the procedure on a set of 70 adult patients with advanced blood cancers, all of whom received a partially matched stem cell donation from an unrelated donor.

The data are “impressive,” Jimenez Jimenez said, particularly since the study enrolled high-risk patients and the average age was 65.

The study was also “very permissive” with the degree of donor mismatch allowed, Jimenez Jimenez said.

Donors had match levels from 4/8 to 7/8 on a scale where 8/8 is a perfect match, researchers said. At match levels of 5/8 or higher, more than 99% of people from a wide range of racial and ethnic groups are expected to find a donor.

The new approach also means that patients often can find higher-quality donations from younger people with healthier stem cells, Jimenez Jimenez said.

These early findings are part of an ongoing phase 2 study that will enroll about 300 patients at more than 30 hospitals, researchers said.

Researchers will present these results at the upcoming annual meeting of the American Society of Clinical Oncology in June. Findings presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.

More information

The National Institutes of Health has more information on graft-versus-host disease.

SOURCE: University of Miami, news release, May 23, 2024