Two studies have found the umbilical cords of newborn babies offer an alternative, albeit last-resort, source of stem cells for adult leukemia patients needing transplants.

They may represent another treatment alternative for people who are quickly running out of options, experts say.

"It's confirmation of something that we've known anecdotally," said Dr. Marshall Lichtman, executive vice president of research and medical programs at the Leukemia and Lymphoma Society, which helped fund the study. "These are two studies that are more formal and have a larger sample of patients. They show that, with careful selection, cord blood can be useful in adults."

"We've done unrelated bone marrow transplants for decades, but the problem has been availability of donors," added Dr. Mary J. Laughlin, lead author of one of the studies and an associate professor of medicine at Case Western Reserve University School of Medicine in Cleveland, Ohio. "This could extend the available donor pool. We have more work to do on the technology, but this will impact practice even today."

Both studies appear in the Nov. 25 issue of the New England Journal of Medicine (news - web sites).

Cord blood, which comes from the placenta and umbilical cord, contains stem cells that can be used to repopulate the bone marrow in certain diseases such as leukemia. The stem cells enable patients to produce healthy blood cells.

Cord blood has the advantage of being non-controversial and does not need to be matched as closely as bone marrow. It is also quickly available through cord blood banks.

"When we try to do a bone marrow transplant with an unrelated donor, on a good day it takes two months," Laughlin said. "Acute leukemia doesn't wait around that long. It takes 10 to 14 days for cord blood."

The problem is that cord blood often doesn't yield enough cells to successfully treat adults, unless they are of small physical size.

"Cord blood has the potential of being a very important additional source for patients who are desperately in need of a hematopoietic stem cell transplant. But, thus far, most of the cord blood samples don't have the sufficient number of stem cells to engraft adults of normal or large size," Lichtman explained.

In children with leukemia, cord blood and bone marrow transplants have been shown to have similar long-term results. There have been no large-scale comparisons in adults until now.

The first study compared treatment data on more than 500 adults with leukemia. The first group of patients underwent cord blood stem cell transplants. They were compared with two other groups: individuals who had fully matched bone marrow transplants from unrelated donors and patients who had partially matched unrelated bone marrow transplants.

The highest survival rates (33 percent) were seen in those patients who underwent bone marrow transplants with matched unrelated donors. The other two groups had survival rates of 22 percent.

The second study compared 584 adults with acute leukemia who received bone marrow with 98 adults who received cord blood, in both cases from unrelated donors.

Again, cord blood was found to be an alternative source of stem cells for people who lacked a matched bone marrow donor.

As an accompanying editorial pointed out, however, in both studies recipients of cord blood were younger, weighed less and were more likely to have advanced leukemia. In the second study, cord blood recipients had slower engraftment. In the first study, recovery among cord blood and mismatched bone marrow recipients was generally slower; the relapse rate was similar in all three groups.

"Cord blood is clearly an option if the adult is small and the nucleated cell count in the cord blood sample has a reasonable probability of producing a successful graft," Lichtman said.

  According to Laughlin, as many as 16,000 leukemia patients diagnosed each year require a bone marrow transplant but can't find a match. It is this group that could potentially benefit from cord blood transplants, she said.