Doctors seem to have found a way to make bone marrow transplants safer and more effective against blood cancers like leukemia, an achievement that offers new hope for people over 50 in particular.
The advance by Stanford University doctors could make such transplants, which have dramatically improved cancer survival among children and young adults, more widely available to older people who typically don't fare as well.
It also brings the field closer to its Holy Grail - training a recipient's body to accept tissue from another person and live a "blended" life without heavy reliance on anti-rejection drugs.
Scientists already had achieved this in mice; Stanford researchers now have extended it to people. Their study is published in Thursday's New England Journal of Medicine and was funded by the National Institutes of Health.
Specialists said the study was small and preliminary, but very promising.
"If it works, we would be able to do transplants in a lot more people," said Dr. Mary Horowitz, scientific director of the Center for International Blood and Marrow Transplant Research, based at the Medical College of Wisconsin, which had no role in the research.
Ideally, a leukemia or lymphoma patient would be given radiation or high doses of chemotherapy to destroy the cancerous bone marrow before receiving healthy marrow or blood stem cells from a donor. However, many patients, especially those over 50, die of infections they are unable to fight off before the new marrow takes hold and grows.
To avoid this problem, doctors usually destroy only part of the patient's original marrow. That brings other dilemmas: some cancerous blood cells remain, and the new marrow frequently attacks the old - an often-fatal problem called graft-versus-host disease.
Stanford researchers developed a way to condition the recipient to accept the new marrow and to inactivate the parts of the patient's immune system that would attack it. They used a combination of low-dose radiation over two weeks and short courses of immune-suppressing drugs.
Only 2 of the 37 patients given the experimental treatment developed severe graft-versus-host disease. Ordinarily, more than half of them would have.
An average of one year later, 27 of the 37 were still alive, and cancer was in complete remission in 24 of them - better results than usual. The average age of the patients was 52.
"It can achieve the cure of the tumor without the high likelihood that you will come down with the dreaded side effect," said the lead researcher, Dr. Samuel Strober.
The results need to be repeated in larger studies, but are "impressive" and "open a new era in the field," Dr. Gerard Socie, a transplant expert from several universities in Paris, wrote in an accompanying editorial.
Patients also need to be followed for longer than a year to see if they remain cancer-free, Horowitz said.
Bone marrow and blood cell transplants are one reason the death rate from childhood cancers has dropped roughly 50 percent since the 1970s. Leukemia is the most common cancer that children face, but it is diagnosed 10 times more often in older adults - the very group for whom transplants have been most dangerous.
With the new treatment, "the side effects are being markedly reduced, which is good news for elderly patients with leukemia and lymphoma," Strober said.
The approach also might help people receiving organ transplants if they are "conditioned" with marrow or blood cells from the donor before receiving a kidney or other organ, Strober said.