WEDNESDAY, Feb. 7 (HealthDay News)-- Compounds called growth factors, given to help cancer patients better tolerate chemotherapy and reduce infection, may actually boost their risk for leukemia or a bone marrow disorder later on, new research suggests.
Even so, the researchers said the findings are not cause for alarm.
"This should not dissuade people from getting growth factors or chemo if their doctors think they need it," stressed oncologist Dr. Dawn Hershman, an assistant professor of medicine and epidemiology at Columbia University Medical Center, in New York City.
The study is published in the Feb. 7 issue of the Journal of the National Cancer Institute.
While the use of growth factors in the study doubled patients' risk of getting acute myelocytic leukemia (AML) or a bone marrow disorder called myelodysplastic syndrome (MDS), Hershman emphasized that the absolute risk was already "very low."
Her team evaluated 5,510 breast cancer patients using a Medicare population-based database of women aged 65 years or older. The women were treated with chemo between 1991 and 1999.
Some women also received a growth factor therapy. Of the total, 906 women received either granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF), or both. The other patients received chemotherapy alone.
In the 48 months after their breast cancer diagnosis, about 1 percent of the women who had chemo alone developed either AML or MDS, while almost 2 percent of those who got chemo and a growth factor treatment did.
Hershman's group decided to focus on growth factors -- which are being used more and more to help patients better tolerate chemotherapy -- because there has been concern among medical experts that the drugs may aid the survival of cells that have been dangerously mutated by chemotherapy.
Typically, these mutated cells would simply die off. But growth factors may actually save these cells and allow them to grow into a cancer such as AML, Hershman explained. Or, the growth factors may lead to MDS, the bone marrow problem.
Cancer patients typically receive growth factors because they boost levels of infection-fighting white blood cells. Chemo destroys these infection-fighting cells, and the body can't quickly replace them.
But, Hershman said, questions remain. It's not certain that the growth factors actually caused the AML or MDS, she said. "It might be that people may be more susceptible to developing leukemia if they were more sensitive to the chemo," she said. "The chemo itself could have caused the leukemia."
The association is certainly "worthy of more research," said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society.
Right now, however, the results "are a not an indication to change the standard of care," he said.
"Your doctor should tell you [growth factors] could cause difficulty later on," Lichtenfeld said. But doctors should also point out that "growth factor drugs have changed the face of cancer chemotherapy," he added. It's also important to note that the study only looked at women aged 65 and older, Lichtenfeld said.
Before these compounds were routinely given, he said, many patients had to be hospitalized as a result of reactions to chemotherapy, or their chemotherapy had to be delayed until they felt better.
Growth factors have been tied in the past to increased risks in breast cancer patients, Lichtenfeld said, but up until now, there was no data to support that suspicion. Hershman's study now provides some proof of a link, he said.
In an editorial accompanying the study, experts form Erasmus University Medical Center Rotterdam in the Netherlands point out that the benefits of chemo may far outweigh any risk of a second cancer.
More information
To learn more about the side effects of chemotherapy, visit the American Cancer Society.
