Bone marrow transplants can be a lifesaver, replenishing the source of blood cells after radiation or chemotherapy destroys it. But for some patients with blood disease, no matching donor can be found. In tomorrow's New England Journal of Medicine, researchers report that transplants of umbilical cord blood--which also contains immature blood cells--can be an effective alternative to marrow, even when the donor and recipient are unrelated.
Small studies had suggested that cord blood transplants could work, so Pablo Rubinstein, research chief at the New York Blood Center, and his colleagues began a larger investigation. They collected information on 562 patients who have received cord blood transplants from unrelated donors since 1992. In more than 80% of recipients, the transplanted cells "engrafted"--took up residence in the bone marrow and started churning out mature blood cells. In addition, less than a quarter of patients suffered severe or fatal "graft versus host disease" (GVHD), a reaction in which the immune cells in the transplanted blood attack the recipient's body. (GVHD afflicts up to 35% of bone marrow recipients.)
The findings suggest it is easier to find a successful match for cord blood transplants. To lessen the chance of GVHD, scientists try to match six types of cell-surface proteins between donor and recipient. Bone marrow transplants require at least five proteins for a match, but Rubinstein and his colleagues report that even in patients where only four match, cord blood cells can engraft without triggering severe GVHD. Scientists still need to sort out whether some mismatches are better than others and how to determine an optimum dose of cord blood for a given patient, says immunologist LeeAnn Jensen of the National Heart, Lung, and Blood Institute in Bethesda, Maryland.
The latest data is encouraging news for patients who cannot find a matching bone marrow donor, says Eric Sievers at the Fred Hutchinson Cancer Center in Seattle. But he points out that as many as 25% of cord-blood patients over the age of 12 failed to engraft, which is often a death sentence. Bone marrow transplants, on the other hand, have up to a 97% engraftment rate. If the technique is to be useful for adult patients, he says, "clearly new ideas are needed."