Blood from a newborn’s umbilical cord, often thrown away but rich in cells that may rebuild the body’s blood production system, is safe to treat leukemia in adults, two studies released Wednesday show.
The studies, published in the New England Journal of Medicine, show that cord blood transplants work even though cord blood does not always restore the immune system as quickly and effectively as bone marrow from a perfectly matched donor.
Cord blood is as effective as slightly mismatched bone marrow, “which is currently accepted as a second-best alternative,” Mary Horowitz of the Medical College of Wisconsin, a chief author of one study, told Reuters.
“This could double to triple the number of adults who get an unrelated transplant,” she said.
Cord blood, which is drained from a newborn’s umbilical cord after it has been cut off, is plentiful and easy to gather. Bone marrow can be collected only through an operation on the donor.
Up to 16,000 people with leukemia who need a transplant fail to get one because they cannot find bone marrow that is a close match, said Cladd Stevens of the New York Blood Center’s National Cord Blood Program.
About 5,000 to 6,000 cord blood transplants have been performed worldwide, most of them on leukemia patients. Only one third of the transplants have involved adults, according to Robert Steinbrook of the New England Journal.
One or two mismatches OK
Doctors rely on a so-called HLA antigen system that gauges how well donated tissue matches the patient’s immune system. A perfect match, usually from a relative, is best. The more HLA mismatches there are, the greater the risk of rejection.
The Horowitz team studied 600 cases and found that it did not matter if there were one or two mismatches in the donated cord blood. The mismatched cord blood rebuilt the immune system as effectively as bone marrow that was mismatched by only one HLA antigen.
The survival rate was 22 percent among patients in those two groups. Where the bone marrow was a perfect match, the survival rate was 33 percent.
The second study, conducted in Europe, compared the results of 584 perfectly matched marrow transplants with 98 cord blood transplants, 92 of which were an HLA mismatch. The success rates between the groups were essentially the same.
The drawback in using cord blood is that, in general, a transplant using it requires “longer to take, and people die when they’re waiting or are more likely to get an infection,” Horowitz said.
“But once it does take, there’s less chance of graft-versus-host disease,” a potentially deadly condition where the immune cells of the transplant attack the body.
One of the biggest hurdles facing cord blood transplant patients is that not every cord blood unit has enough cells for adults, Horowitz said.
The difficulty of getting enough cells is why the treatment has been more common in children, who require fewer cells to rebuild blood and immune systems.
Other research is beginning to show that blood can be combined from two umbilical cords. But there are concerns about the possibility that the cells from the two cords will attack each other.
Nonetheless, initial tests in animals and humans seem to suggest that some units of cord blood can be combined and, when that happens, the blood supply is rebuilt faster. The cells from one of the donors eventually becomes dominant.