Stem cell transplantation following chemotherapy can extend survival and potentially cure certain advanced cancers. Although these demanding procedures were once considered too risky for older patients, advances in transplant methods are challenging that assumption.
“In transplants involving donor cells, there was concern that older patients wouldn’t be able to tolerate the high doses of chemotherapy traditionally used,” explains Joseph Antin, MD, chief of the Adult Stem Cell Transplantation Program at Dana-Farber/Brigham and Women’s Cancer Center (DF/BWCC)
“Older patients were also thought to be more at risk from graft-versus-host disease,” a sometimes severe condition in which immune system cells in the transplanted tissue attack the patient’s own tissue, Antin adds.
Now, due largely to the development of reduced-intensity transplants, which use lower doses of chemotherapy than standard transplants, greater numbers of older people nationwide are getting transplants. At Dana-Farber, for example, 1,627 patients 55 and older underwent transplants between 2011 and 2015, compared to 964 between 2006 and 2010.
Reduced-intensity transplants, in turn, came about because of an unexpected benefit of transplants themselves.
“The original concept behind transplants was to treat patients with high doses of chemotherapy, and sometimes radiation therapy, to wipe out the bone marrow, where hematological cancers like leukemia and lymphoma form,” explains Antin. “The heavy doses not only killed diseased stem cells in the marrow, but healthy ones as well. Transplanting stem cells from a compatible donor rescued the patient from the loss of healthy tissue.” (The transplanted cells, formally known as hematopoietic stem cells, give rise to all the blood cells within the body, including red blood cells that transport oxygen and carbon dioxide, and white blood cells, which defend against disease.)
As doctors gained experience with the transplants, they discovered that the donated cells were more than just a replacement for destroyed bone marrow: They were effective leukemia and lymphoma fighters in their own right. That suggested it may be possible to treat patients with lower doses of chemotherapy and allow the transplanted cells to finish the job of killing the cancer cells.
The introduction of lower-dose, or reduced-intensity, procedures made transplants available for the first time to older patients – generally 55 and older – with hematological cancers or other blood-related conditions. Researchers are working to improve such transplants by bolstering the anti-cancer prowess of donated stem cells to, in effect, achieve the benefits of high-dose approaches with the milder side effects associated with lower-dose therapies.