Mammographic density and risk of breast cancer

Women who have a breast density of 75 percent or higher on a mammogram have a risk of breast cancer that is four to five times greater than that of women with little or no density, making mammographic breast density one of the strongest biomarkers of breast cancer risk.

At the American Association for Cancer Research 101st Annual Meeting 2010, held in Washington, D.C., April 17-21, researchers will present the latest data on mammographic density and breast cancer risk.

"These abstracts strengthen the observation that high breast density is associated with increased risk for breast cancer, and they strengthen the hypothesis that under some conditions, reducing breast density may be associated with reduced risk for breast cancer," said Carol J. Fabian, M.D., professor of medicine in the division of clinical oncology and director of the Breast Cancer Prevention Center at the University of Kansas Medical Center.

Mammographic density refers to the amount of white or radiodense area compared to the amount of grey or radiolucent area on a mammogram. The radiodense area is reflective of the amount of ductal and lobular epithelium, connective tissue and fluid in the breast. The radiolucent area is reflective of the amount of fat in the breast.

While increased breast density is a known risk factor for breast cancer, having a lower breast density doesn't necessarily mean a low risk of developing breast cancer, according to Fabian. Other risk factors are at play, and mammographic density is one tool to help determine a women's risk.

"The cancer research community is always looking for new methods to better define short-term risk to supplement the known risk factors for breast cancer like family history, genes associated with hereditary breast cancer, reproductive variables and age," said Fabian. "Modifiable risk biomarkers like mammographic density are increasingly being used in small early phase prevention trials to help us decide which interesting strategies should be carried further into very large Phase III studies with cancer incidence as an endpoint."

The AACR has highlighted the following abstracts on new research in mammographic density, which will be presented at the Annual Meeting:

4828. Longitudinal breast density and risk of breast cancer
Embargo: 3:55 p.m. ET., April 20, 2010

Women who have a decrease in breast density over a six-year period may have a decreased risk of developing breast cancer compared with women whose breast density remained stable.

"A decrease in breast density appears to be associated with a lower breast cancer risk, and importantly, this result takes into account baseline breast density, as well as changes in BMI that occurred between mammographic assessments," said lead researcher Celine M. Vachon, Ph.D., associate professor of epidemiology in the College of Medicine at the Mayo Clinic, Rochester, Minn.