SEATTLE — The most common method of extracting cells from unrelated donors for patients needing bone-marrow transplants should change in light of new research revealing higher complication rates than an older approach, said the head of clinical research for the Fred Hutchinson Cancer Research Center.

Significant new research published Thursday in the New England Journal of Medicine — the first large, randomized study comparing the two sources of bone-marrow stem cells — showed patients who received transplants from unrelated donors’ blood were significantly more likely to get a complication known as chronic graft-versus-host-disease than those who received cells from donors’ pelvic bones.

In an editorial accompanying the study, Dr. Fred Appelbaum, director of clinical research at the Hutch, said the blood-extraction method supplanted the traditional pelvic-bone extraction method about a decade ago. It is now used in more than three-quarters of the unrelated-donor transplants for patients with such blood malignancies as leukemia or lymphoma.

The complication, short-handed as GVHD, means the transplant recognizes the patient’s tissues as foreign objects and attacks them. The condition can be relatively mild, or severe and debilitating.

“While this study should change practice, it will be interesting to see if it really does,” Appelbaum wrote in his editorial. “The benefits of peripheral blood are seen early, under the watchful eyes of the transplant physician, while the deleterious effects occur late, often after the patient has left the transplant center.”

About 5,500 unrelated donor transplants were done in the U.S. last year, and about 20 million potential unrelated donors are typed and listed in the registries worldwide.

The study, led by a former Hutch transplant physician, Dr. Claudio Anasetti, now at the H. Lee Moffitt Cancer Center in Tampa, Fla., looked at short- and long-term survival, transplant success and complications, both acute and chronic.

Patients survived equally well on both types of transplants, and the peripheral blood-derived grafts began doing their job faster and engrafted more reliably.

But GVHD can cause skin rashes, diarrhea and liver problems, sometimes up to three years after the transplant.