A 4-year-old Virginia Beach boy has received a rare transfusion of blood collected at birth from the umbilical cord of his newborn sister in an unusual attempt by doctors at Johns Hopkins Oncology Center to regenerate his bone marrow and cure him of leukemia. The procedure, known as a cord-blood transplant, was performed Aug. 13. It is designed to work much like a bone marrow transplant but was performed instead of a bone marrow operation because of the baby's age.

In a cord-blood transplant, umbilical and placental blood rich in stem cells that make up the bone marrow were donated to the boy, who first received high doses of drugs that destroyed his cancerous bone marrow. If the procedure succeeds, the stem cells from the cord blood would migrate to the bones and multiply, forming healthy new marrow.

The procedure has been performed successfully three times, twice in France and once in Cincinnati, as a treatment for another blood disorder. Hopkins officials say it is the first time it has been used to treat leukemia, a cancer of the blood.

The 4-year-old, Michael Sancilio, was diagnosed last spring with juvenile chronic myelogenous leukemia, a disease that progresses rapidly, is resistant to drug therapy and is usually fatal within one year.

Other relatives were ruled out as potential bone marrow donors because of immunological incompatibilities. Because of the possibility that the boy's unborn sister would be a match, blood from the placenta and umbilical cord was collected and saved during her birth last June. Subsequent tests revealed that the infant, Christina, is a perfect match.

"We felt in this case that if the stem cells didn't take, we could have the option of obtaining bone marrow later," said John Wagner, a pediatric oncologist who performed the procedure. "This allowed time for {Christina} to get larger and older." To date, the youngest bone marrow donor, Hopkins officials say, was 5 months old.

Michael Sancilio will remain hospitalized for at least a month. Hospital officials say signs of success for the transplant might be seen as early as this week.