Dense breasts, hormones both risk factors

WASHINGTON, Aug. 21 (UPI) -- The density of a woman’s breast tissue and her level of sex hormones are strong and independent risk factors for breast cancer, a U.S. study found.

Study co-author Celia Byrne of the Georgetown University Medical Center in Washington, led a team of researchers at Georgetown University and Harvard University, said the findings are contrary to the belief of many in healthcare that the risk associated with dense breasts merely reflects the same risk associated with high levels of circulating sex hormones.

The study, published in Journal of the National Cancer Institute, found that the relative risk of developing breast cancer in post-menopausal woman with dense breasts was 400 percent higher than in women with fatty, non-dense breast tissue, while high versus low levels of hormones -- estrogen and testosterone -- increased the relative risk by 200 percent. Adjusting for a woman’s circulating hormone levels didn't reduce the risk associated with the level of breast density.

In addition, these two independent risk factors seemed to have additive effects so if a woman had both dense breasts and excess hormones, her risk was increased by 600 percent, the study said.