Breast density should be a factor in assessing breast cancer risk and recommending supplemental imaging, but not the primary factor, according to a study of women who were screened for the disease.
Dr. Cecil Fox/National Cancer Institute
“Counseling strategies that identified women for supplemental imaging based on breast density and BCSC 5-year risk were more efficient compared with strategies based on age and density or density alone,” wrote Karla Kerlikowske, MD, of the Department of Veterans Affairs, and her coauthors. The study was published in JAMA Internal Medicine.
To assess breast cancer risk and strategies for recommending supplemental screening, the researchers assembled a cohort of 638,856 women aged 40 to 74 years who received mammograms at Breast Cancer Surveillance Consortium (BCSC) facilities from Jan. 3, 2005, to Dec. 31, 2014. Participants were identified as high risk via combinations of Breast Imaging Reporting and Data System (BI-RADS) breast density, BCSC 5-year breast cancer risk, and age.
Women with dense breasts made up 47% of those screened, and 60% of those with advanced cancers. Low advanced cancer rates (less than .61 per 1,000 mammograms) occurred in 34.5% of women with dense breasts, while high advanced cancer rates (greater than or equal to .61 cases per 1,000 mammograms) occurred in women with heterogeneously dense breasts and a 5-year risk of 2.5% or higher (6.0% of screened women) and those with extremely dense breasts and a 5-year risk of 1.0% or higher (6.5% of screened women).
In a hypothetical cohort of 100,000 women, supplemental imaging for all 47,012 women with dense breasts would mean a ratio of 1,866 supplemental imaging discussions per potential advanced breast cancer prevented. If imaging was considered based on a combination of density plus BCSC 5-year risk, the number of women screened would be reduced to 12,506 and the ratio would become 1,097 supplemental imaging discussions per potential advanced cancer prevented.
The coauthors acknowledged their study’s limitations, including their lack of ability to determine if women at high risk of advanced cancer would benefit from supplemental screening. In addition, they were unable to evaluate digital breast tomosynthesis outcomes, though they noted that, to their knowledge, “no published evidence indicates that advanced cancer rates differ for digital mammography vs. tomosynthesis according to breast density.”
The study was funded by the Patient-Centered Outcomes Research Institute, the Breast Cancer Surveillance Consortium, the National Cancer Institute, the Agency for Health Research and Quality, and the Lake Champlain Cancer Research Organization. The authors reported several potential conflicts of interest, including being members of various working groups, advisory boards, committees, task forces, and panels.
SOURCE: Kerlikowske K et al. JAMA Intern Med. 2019 Jul 1. doi:10.1001/jamainternmed.2019.1758 .