Stem Cell Transplants More Effective Than Bone Marrow
Dec. 6, 1999 (Tuscaloosa, Ala.) -- Results of the largest study ever to compare outcomes of cancer patients transplanted with bone marrow vs. stem cells are "promising news for many patients with high-risk blood cancers," says lead researcher William Bensinger, MD, at the 41st Annual American Society of Hematology meeting in New Orleans.
"The evidence is convincing enough that we've already made a change in treating our high-risk patients," says Bensinger, a professor of medicine at the Fred Hutchinson Cancer Research Center in Seattle. "For patients with accelerated phase chronic myelogenous leukemia (CML), or acute myelogenous leukemia (AML), and for acute lymphoblastic leukemia (ALL) who are beyond first remission or who have had nonresponsive relapses, we are using stem cells."
Stem cell transplantation differs from bone marrow transplantation in that the transplanted cells are removed from the circulating blood instead of the bone.
In the three-year, multicenter study, more than 160 patients with a variety of blood cancers were randomly assigned to receive bone marrow or stem cells transplants. The two-year survival rate among the marrow transplant patients was 45%, compared to 70% for the stem cell patients.
"The results are exciting because most strategies aimed at reducing relapse are associated with higher toxicities, more complications, and higher mortality," Bensinger tells WebMD. "This data suggests that stem cell transplants may offer the best of both worlds -- fewer relapses with fewer complications."
Bensinger says the advantage of stem cells over marrow transplants for low-risk patients remains in doubt because not enough data have been gathered to draw conclusions. He also emphasizes that since the study is based on preliminary data, there are several reasons to be cautious about the results.
"First, there isn't enough evidence to say that stem cells are better than bone marrow," says Bensinger. "There is a trend that favors stem cells but it is not statistically significant yet."
Another reason to be cautious, he says, is that other studies suggest that stem cell patients have higher rates of chronic graft vs. host (GVH) disease, which may not occur until three to five years after transplant, he warns. "We won't know for another year or two if chronic GVH disease shows up among these patients," he says.
GVH disease occurs when cells in the transplanted marrow attack the transplant recipient's tissues. About one-third of those who get the disease will die.
Further good news from the Fred Hutchinson Cancer Research Center involved another study that shows promise for older, more debilitated patients who can't handle the large doses of chemotherapy that usually go along with stem cell transplants.
Patients were given immune-suppressing chemotherapy and then received a stem cell transplant from a matched family donor. More than 50 such transplants have been performed. Preliminary results indicate that the transplant is well tolerated even in older or debilitated patients.
"My colleagues call this new therapy 'minitransplants' because patients are given smaller doses of stem cells after low-dose total-body irradiation combined with potent immune suppressants. It's a promising treatment," says Bensinger.