Not all women with dense breasts are at high enough risk for breast cancer to justify additional imaging after a normal mammogram, according to a study published in Annals of Internal Medicine (2015; doi:10.7326/M14-1465). Women with specific types of dense breasts who also have a high 5-year cancer risk should discuss supplemental screening strategies with their doctors.

Having dense breasts puts women at higher risk for cancer and makes it more difficult to detect cancer using digital mammography. Many states have laws requiring that women be notified if they have dense breasts and be advised that they should discuss additional screening with their doctor. While supplemental imaging may increase cancer detection, it also may increase false-positive rates.

Researchers studied screening data from the Breast Cancer Surveillance Consortium (BCSC) to determine which women with dense breasts might benefit from supplemental screening to detect cancer that may have been missed on mammography. The data examined included 365,426 women age 40 to 74 years who had 831,455 digital screening mammography examinations.

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They found that more than half of women with extremely dense breasts did not have a high risk for interval cancers, or aggressive cancers diagnosed within 12 months after a normal mammogram. Among 51% of women with heterogenously dense breasts and 52.5% with extremely dense breasts, 5-year risk was low-to-average (0 to 1.66%).

Interval cancer rates were highest among women with extremely dense breasts and a BCSC-calculated 5-year breast cancer risk of 1.67% or greater and women with heterogeneously dense breasts and a BCSC-calculated 5-year risk of 2.50% or greater.

The authors of an accompanying editorial (doi:10.7326/M15-0821) wrote that these findings provide compelling evidence that breast density should not be the sole criterion to guide decisions about supplemental breast cancer screening. They suggest that federal legislation on the management of screening in women with dense breasts is premature and that resources should instead focus on identifying women at high risk for interval breast cancer. They stated that no consensus has been reached on the optimal approach to supplemental imaging in women with dense breasts.