Leukaemia advance proves safe

BOSTON - 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 leukaemia in adults, research shows.

Two 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", said Mary Horowitz of the Medical College of Wisconsin, a chief author of one study.

"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.

In New Zealand, stem cells from 2000 babies are held for future medical uses at CordBank, a private cord blood storage facility in Auckland.

Bone marrow can could be collected only through an operation on the donor.

Cladd Stevens, of the New York Blood Centre's National Cord Blood Programme, said up to 16,000 people with leukaemia who needed a transplant failed to get one because they could not find bone marrow that was a close match.

About 5000 to 6000 cord blood transplants have been performed worldwide, most of them on leukaemia patients.

Only one third of the transplants have involved adults, says Robert Steinbrook of the New England Journal.

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 per cent among patients in those two groups. Where the bone marrow was a perfect match, the survival rate was 33 per cent.

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", Dr 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 was that not every cord blood unit had enough cells for adults, Dr 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. -REUTERS