New study examines potential impact of breast density notification legislation in U.S. women

Mammographically-dense breasts - those that show more breast and connective tissue versus fat in a mammogram image - are recognized as a risk factor for developing breast cancer and can also hamper an accurate reading of a mammogram. National legislation currently under consideration would require the disclosure of mammographic breast density information to women with dense breasts, as well as encourage the consideration of supplemental screening for those women. To date, the prevalence of women with high mammographic breast density in the U.S. has been largely unknown, making the impact of such legislation hard to quantify.

Now for the first time, a new study published in the September 2014 Journal of the National Cancer Institute (JNCI) and led by Brian Sprague, Ph.D., a University of Vermont assistant professor of surgery and member of the Vermont Cancer Center, estimates the number of women in the United States for whom breast density notification legislation would potentially impact. The study was conducted with the National Breast Cancer Surveillance Consortium and utilizes data from breast cancer screening registries based at the University of Vermont, the Group Health Research Institute (Seattle, WA), the University of North Carolina, Dartmouth's Geisel School of Medicine, the University of California-San Francisco, and the University of New Mexico.

Given their findings, Sprague and his research team are asking policy makers to consider the large number of women who fall into the category of having mammographically-dense breasts in the U.S. as they debate breast density notification legislation and screening recommendations.

Radiologists rate breast tissue density through mammography using four established categories: "almost entirely fat," "scattered fibroglandular densities," "heterogeneously dense," and "extremely dense." Legislation already in place in states such as California, New York and Massachusetts, and laws being considered at the federal and state levels, define mammographically-dense breasts as those rated "heterogeneously dense" or "extremely dense."

Sprague's study estimates a high prevalence of mammographically-dense breasts in the U.S. in women ages 40 to 74 years old with nearly 28 million women, or 43 percent of all women in that range, being rated as having either heterogeneously or extremely dense breasts. Sprague and his team note that given the lack of evidence regarding the effectiveness of supplemental screening approaches such as ultrasound and MRI, and the number of false positives associated with some of these screenings, policy makers and clinicians need to work to ensure that women receiving dense breast notification have opportunities to evaluate risk, discuss evidence, and pursue effective supplemental screenings where appropriate.

Sprague and his team found that nearly 45 percent of the overall 27.6 million women in the U.S. estimated to have dense breasts fall into the 40 to 49 age range. Results from the study, which used data from more than 1.5 million mammograms taken over a four-year period, were also consistent with prior studies demonstrating strong inverse associations of age and body mass index (BMI) with mammographic breast density (as age increases and BMI increases, mammographic breast density decreases).

"This large-scale study estimating the number of women with mammographically-dense breast tissue provides a strong case for broader considerations around any breast density notification legislation, as well as any subsequent recommendations for risk assessment and/or additional screenings for affected women," says Sprague, who is also principal investigator for the Vermont Breast Cancer Surveillance System within the University of Vermont Office of Health Promotion Research.

SOURCE University of Vermont