Umbilical-cord blood, now used mostly to treat children with leukemia, could save thousands of adults with the disease each year who cannot find bone marrow donors, two big studies indicate.

A European study found that those who got cord blood were just as likely to be free of leukemia two years later as those who got marrow. A U.S. study looking at three-year survival yielded results almost as promising.

To Dr. Mary Horowitz of the Medical College of Wisconsin, senior author of the U.S. study, the message is clear: Umbilical cord blood can save adults.

Leukemia patients often undergo radiation or chemotherapy to kill their cancerous white blood cells — a treatment that wipes out their immune systems, too. To restore their immune systems, doctors give these patients an infusion of bone marrow or umbilical cord blood, both of which contain stem cells capable of developing into every kind of blood cell.

Cord blood offers an important advantage over marrow that makes it particularly valuable for use in transplants: Its stem cells are less likely to attack the recipient's body. That allows a wider margin of error in matching up donors and recipients.

But up to now, cord blood has been considered suitable only for children, because each donation has only about one-tenth the number of stem cells in a marrow donation.

The two new studies, published in Thursday's New England Journal of Medicine, suggest that is not a serious impediment.

In the European study, involving 682 patients, about one-third of both those who got matched marrow and those who got cord blood that did not quite match their own tissues were alive after two years. In the U.S. study of 601 patients, about one-third of those who got matched marrow were leukemia-free after two years, compared with about one-fifth of those who got cord blood or unmatched marrow.

Both studies were based on records from transplants in the late 1990s and early 2000s.

Using cord blood could improve the odds of getting a transplant for the 16,000 U.S. adult leukemia patients each year who cannot find a compatible marrow donor, said the U.S. study's leader, Dr. Mary J. Laughlin of Case Comprehensive Cancer Center in Cleveland.

Still, Dr. Nancy Kernan, assistant chief of marrow transplantation at Memorial-Sloan-Kettering Cancer Center in New York, said cord blood transplants in adults should be done only as part of studies to look at and improve their effectiveness.

Public cord blood banks — where blood drawn from umbilical cords and placentas at birth is kept frozen — need to quadruple their supply to find a match for every leukemia patient who needs one. With 4 million births a year in this country, and most cord blood thrown away, that should not be a problem once more public money comes into play, doctors said.

A federal Institute of Medicine committee is already looking into the best way to set up a national cord blood supply, and is scheduled to complete its report in March.

"I know our committee will consume this study avidly," said Kristine Gebbie, chairman of the group.

The first bone marrow transplants were done in the 1960s; cord blood transplants started in the 1990s. Stem-cell transplants save only 20 percent to 30 percent of the patients who hope to grow new immune systems. But without the treatment, virtually all of them would die.

Some researchers said techniques they have developed in the past two years, since the study ended, already have boosted their success.

Most doctors consider cord blood more appropriate for smaller people, because it contains fewer stem cells than marrow. In the two studies, cord blood recipients tended to weigh less than those who got marrow — an average of 22 pounds less in the U.S. research, about 18 in the European study.

  There are two competing U.S. public cord bank systems, one holding about 38,000 vials, the other 27,000. Together, they do not add up to the supply kept by just one of the 20 or so private banks kept for paying families.