March 2, 2011

Obesity May Increase Risk of Breast Cancer

(Ivanhoe Newswire) "“ Obesity and inactiveness may increase the risk of triple-negative breast cancer, a subtype of breast cancer characterized by lack of estrogen, progesterone, and HER2 expression. Triple-negative breast cancers account for about 10 to 20 percent of all breast cancers and are associated with an extremely poor prognosis because of the lack of targeted drug therapies.

"Breast cancer is not just one disease. It is a complex combination of many diseases," Amanda Phipps, Ph.D., a postdoctoral fellow at the Fred Hutchinson Cancer Research Center, was quoted as saying. "The fact that we found an association with triple-negative breast cancer is unique because, biologically, this subtype is very different from other breast cancers."

Epidemiologists have always noted a link between obesity and increased risk of postmenopausal breast cancer, as well as a decreased risk that comes with more physical activity. A relationship between adipose tissue and estrogen is thought to contribute to the risk.

Phipps and colleagues analyzed data from the 155,723 women enrolled in the Women's Health Initiative. They assessed levels of baseline body mass index (BMI) and recreational physical activity among the 307 women who had triple-negative breast cancer and the 2,610 women who had estrogen receptor-positive breast cancer.

Results showed that women with the highest BMI had a 35 percent increased risk of triple-negative breast cancers and a 39 percent increased risk of estrogen receptor-positive breast cancers. Those who reported high rates of physical activity had a 23 percent decreased risk of triple-negative breast cancer and a 15 percent decreased risk of estrogen receptor-positive breast cancer.

SOURCE: Cancer Epidemiology, Biomarkers & Prevention, published online March 1, 2011