By Will Boggs MD
NEW YORK (Reuters Health) - 2/7/2019
Breast-density notification combined with breast-cancer risk helps identify women at high risk of advanced breast cancer who might benefit from supplemental imaging, according to an analysis of Breast Cancer Surveillance Consortium (BCSC) registry data.
"Discussions of supplemental imaging in women with dense breasts should be combined with evaluating breast-cancer risk, given 50% of women with dense breasts are at low breast-cancer risk," said Dr. Karla Kerlikowske of the University of California, San Francisco, and the Department of Veterans Affairs, San Francisco.
"Providing information on breast density alone without considering breast-cancer risk does not allow for the most informed clinical decisions to be made about appropriate use of supplemental imaging," she told Reuters Health by email.
Supplemental screening for breast cancer might benefit women with dense breasts who are at increased risk of interval and advanced breast cancer, and most states now require some level of notification on screening mammography reports of breast density.
The American College of Radiology suggests that supplemental ultrasonography may be useful in women with dense breasts as the only risk factor, while the U.S. Preventive Services Task Force has found insufficient evidence to assess the balance of benefits and harms of supplemental screening in such women.
Dr. Kerlikowske's team used data from more than 638,000 women in an effort to identify the most efficient strategy for targeting women for supplemental-imaging discussions.
Women with dense breasts accounted for 47.0% of screened women and 60.0% of advanced cancers, the team reports in JAMA Internal Medicine, online July 1.
Higher advanced-cancer rates (0.61 or more cases per 1,000 mammograms, based on literature benchmarks) were seen in 6.0% of screened women with heterogeneously dense breasts and a five-year BCSC cancer risk of 2.5% or higher and in 6.5% of screened women with extremely dense breasts and a five-year BCSC cancer risk of 1.0% or higher. Together, these groups comprised 27.1% of advanced cancers.
Women with any BI-RADS density and five-year BCSC risk less than 1.0% (which included 29.5% of screened women) had the lowest advanced-cancer rates and screen-detected early-cancer rates.
Breast density plus BCSC five-year risk was the most accurate strategy (AUROC, 0.642) for identifying women at risk of advanced breast cancer.
Using this combination strategy would result in 1,097 supplemental imaging discussions per potential advanced-cancer prevented, compared with 1,866 with supplemental imaging for all women with dense breasts.
"Women should be informed of their specific BI-RADS breast density category," Dr. Kerlikowske said. "It is not sufficient to inform them they have dense or nondense breasts. Women need to know whether their breasts are almost entirely fatty, scattered fibroglandular densities, heterogeneously dense, or extremely dense."
"Informing women of their specific breast-density category would allow women the opportunity to seek out published and online information about their specific density category, be better positioned to discuss the clinical impact of breast density on screening strategies, and make more informed choices with their healthcare providers," she said.
"In discussions of supplemental imaging with women at high risk of advanced disease, these women are also at high risk of a false-positive biopsy," Dr. Kerlikowske added. "Women at high risk of advanced disease need to decide if the potential of detecting advanced disease early with supplemental imaging is outweighed by the more than 10-fold greater chance of a false-positive biopsy."
Dr. Ilana B. Richman from Yale School of Medicine, in New Haven, Connecticut, who co-authored and invited commentary related to this report, told Reuters Health by email, "One key takeaway from this paper is that although breast density has gotten a lot of attention recently, it is not the only important risk factor for a late-stage diagnosis. Indeed, women with dense and nondense breasts can be at similar risk of a late stage diagnosis, depending on other risk factors."
"So it may be important to take a holistic view of breast-cancer risk when considering supplemental screening, rather than only focusing on breast density," she said.
"Even when restricting screening to the highest-risk group, more than 1,000 women would have to be screened to prevent one late-stage cancer, and this is assuming that supplemental screening actually prevents all late stage cancers," Dr. Richman said. "In lower-risk groups, the number of women who must be screened is even higher."
"Given this, one key question that emerges is whether this focus on supplemental screening is somewhat misplaced," she said. "Doctors and patients both have limited resources, and there is an opportunity cost associated with any medical decision. When we focus on supplemental screening, does something else get ignored? For some patients, it may make sense to focus on some other aspect of their health care or preventive care that is more likely to benefit them rather than supplemental screening."
JAMA Intern Med 2019.