The new technique turns the treatment upside down. Traditionally, the transplants have been used to replenish the bone marrow after it has been wiped out by the intense chemotherapy or radiation used to kill tumors. Now the transplants themselves are being used to fight the tumor. It uses radiation and drug treatment so mild that most patients go home after treatment -- and none suffer the hair loss, nausea, or painful mouth sores typical of more intensive cancer treatments.
This is good news for older patients who usually are too weak to survive normal stem cell therapy.
"Patients should not just be put on the shelf because they are older," lead study author Peter A. McSweeney, MD, tells WebMD. "The toxicity of this now is low enough that [more frail] patients may in fact be candidates for potentially curative therapies."
But the new treatment isn't without serious, life-threatening risks. The donor cells contain immune cells that attack the tumor. To let them do their job, less potent immune-suppressing treatment is used -- but this can let the new cells get out of control and attack the patient, a phenomenon called graft-vs.-host disease or GVHD.
In older patients, this is a potentially new treatment for a variety of cancers," McSweeney says. "It adds a therapy which risks a fair amount of toxicity from GVHD and adds a realistic possibility of actually eradicating these fatal diseases."
McSweeney, director of bone marrow transplantation at the University of Colorado Health Science Center in Denver, is developing the new treatment along with researchers from Seattle's Fred Hutchison Cancer Center; Stanford University in California; and the University of Leipzig in Germany.
The researchers treated 45 patients with a wide range of blood tumors, including leukemia, lymphoma, and multiple myeloma. All of the patients were too old or too frail for conventional bone marrow transplant. All received cells donated by a brother or sister whose immune cells matched those of the patient. Some also received additional infusions of donated immune cells after the first transplant.
After more than one year, two-thirds of the patients remained alive. More than half of the patients were in complete remission. Eight patients -- five with chronic myelocytic leukemia or CML and three with chronic lymphocytic leukemia or CLL -- had no detectable cancer up to 12 months after transplant.
"I think this very interesting work is a clear demonstration that the more important aspect of this kind of transplant is the graft-vs.-tumor effect rather than repopulating the bone marrow," Harmon Eyre, MD, chief medical officer for the American Cancer Society, tells WebMD. "It opens the treatment up to older patients who would never have had this available. It represents a true advance in this whole field."
Ivan Borello, MD, assistant professor of oncology at Johns Hopkins University, is working on a different way to stimulate antitumor immunity by using a person's own cells as stem cell transplants. He praises the McSweeney team's work as the cutting edge of research into transplants from matched donors.
"Their idea is to take advantage of the immunological aspect of marrow transplants," Borello tells WebMD. "It is a good first step, but we don't know the long-range effects, and the risk is that over time we will see more GVHD in these transplants."
McSweeney agrees, and notes that new studies already are under way. Some of these studies, he says, are using transplants from unmatched donors.