Umbilical cord blood transplants may be a viable treatment option for adults with leukemia when a matching bone marrow donor isn’t available, according to two major new studies.

Umbilical cord blood transplants (search) are already successful in treating children with leukemia, but until now the safety and effectiveness of the treatment in adults with leukemia (search) has not been examined.

A common treatment for adult leukemia (search) is a stem cell bone marrow transplant (search). During this procedure diseased bone marrow cells are replaced with healthy, immature cells known as stem cells. These stem cells are taken from a strictly matched blood marrow donor. Once transplanted into the leukemia patient, these cells can grow into normal blood cells.

However, only about 30 percent of eligible adults with leukemia have a family member that matches or is a compatible bone marrow donor. Of the remainder, nearly 20 percent receive transplants from unrelated donors, but the risk of the recipient rejecting the bone marrow transplant, because of incompatibility, is higher when an unrelated donor is used.

Stem cells that can be used in such a transplant are also found in umbilical cord blood. But cord blood transplants have been used only as a last resort in adults with leukemia because cord blood contains only a small fraction of stem cells needed to treat an adult.

But two new studies published in this week’s New England Journal of Medicine indicate that cord blood from an unrelated donor should be considered as an alternative source of stem cells for treating adults with leukemia when a matching bone marrow donor is not available.

Umbilical Cord Blood vs. Bone Marrow Transplants

In the studies, researchers compared the results of stem cell transplants using stem cells taken from unrelated bone marrow donors with stem cells taken from unrelated cord blood donors.

In the first study of 663 adults, 98 received cord blood and 584 received bone marrow in transplants performed from 1998 through 2002.

The results showed that adults who received cord blood transplants had a lower risk of severe rejection of the donor cells (a condition known as graft-versus-host disease) than those who had bone marrow transplants, but immune system recovery was significantly delayed.

Overall, there were no significant differences in the risks of leukemia relapse, or death between the two groups.

In the second study, researchers compared the results of partially matched versus unmatched cord blood and bone marrow transplants.

The study showed that recovery was slower among those who got cord blood stem cell transplantation or mismatched bone marrow than those who got the matched bone marrow transplants.

The risk of treatment failure and death were also lowest among those who got matched bone marrow transplants.

But people who got mismatched bone marrow or mismatched cord blood had about the same risk of death or treatment failure, and the relapse rate was similar among all the groups.

New Option in Adult Leukemia Treatment

In an editorial that accompanies the studies, Miguel A. Sanz, MD, PhD, of the Hospital Universitario La Fe in Valencia, Spain, says that the results of these studies show that cord blood transplantation is a realistic alternative for the treatment of leukemia in adults.

“Both reports reinforce the role of cord blood transplantation in the treatment of adults with leukemia,” writes Sanz. “However, neither group recommends cord blood transplants over HLA-matched marrow from unrelated donors in adults, even though in children, cord blood transplantation is now often used as an alternative to HLA-matched bone marrow from unrelated donors.”

Sanz says both groups of researchers agree that cord blood should be used if a matched bone marrow donor is not available within a reasonable time.

Although umbilical cord blood may be increasingly used as a treatment for diseases in children and adults, another report published in the same journal highlights the controversies surrounding the private and public cord blood banks in the U.S.

“The structure of a national cord blood program in the United States remains uncertain,” writes Robert Steinbrook, MD, a correspondent forThe New England Journal of Medicine. “In many instances, the private storage of umbilical cord blood is not worthwhile.”

By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCES: Laughlin, M. Rocha, V. The New England Journal of Medicine, Nov. 25, 2004; vol 351; pp 2265-2275: 2276-2285.