Large Study Finds Elevated 10-Year Breast Cancer Risks in Women with Dense Breasts and Benign Breast Disease

A new study of over 3.9 million Korean women found that the combination of benign breast disease and dense breasts led to elevated 10-year risks for the development of breast cancer.

In a retrospective review drawing from the National Health Insurance Service-National Health Information Database (NHIS-NHID) in Korea, researchers assessed 3,911,348 Korean women who had mammography screening between January 2009 to December 2010. Study participants who had normal breasts (Breast Imaging Reporting and Data System (BI-RADS) category 1) or benign breast disease (BI-RADS category 2) at the time of this screening were included in the study, which was recently published in Radiology.

Among the 58,321 women who developed breast cancer during a median follow-up of 10.6 years, researchers found a higher proportion of benign breast disease (18.4 percent) and dense breasts (55.4 percent) at the baseline screening in comparison to those who did not develop breast cancer (13.3 percent and 38.4 percent respectively).

Women who had no breast disease and BI-RADS category A breast density (almost entirely fatty tissue) at the baseline screening had a .73 percent risk of breast cancer at 10 years, according to the study. In contrast, the study authors noted a 2.18 percent risk for women who had baseline benign breast disease and BI-RADS category C breast density (heterogeneously dense) and a 2.64 percent risk for the combination of benign breast disease and BI-RADS category D breast density (extremely dense) at 10 years.

In other words, patients who had a combination of benign breast disease and BI-RADS category C or BI-RADS category D (extremely dense) breast density had a nearly threefold or greater 10-year risk for breast cancer in comparison to women who had no breast disease and BI-RADS category A breast density.

“Our findings strengthen the evidence suggesting that benign breast disease and breast density are important factors that should be carefully considered when stratifying breast cancer risk and should be incorporated in future breast cancer risk models,” wrote senior author Boyoung Park, M.D., Ph.D, who is affiliated with the Hanyang University College of Medicine in Seoul, Korea, and colleagues.

In a subsequent subgroup analysis, Park and colleagues found the combination of breast density and benign breast disease was associated with higher risks for developing invasive breast cancer and ductal carcinoma in situ (DCIS).

Given the overall findings of the study, the authors suggested that supplemental screening could be beneficial for this patient population and noted recent studies on the topic, including one study that found supplemental magnetic resonance imaging (MRI) in comparison to mammography alone reduced interval cancers in women with BI-RADS category D breast density in a two-year screening period.

In regard to study limitations, Park and colleagues noted no biopsy results were available from the NHIS-NHID database utilized for the study. As per the Korean national cancer screening guidelines, the study authors pointed out that further workup and periodic mammography screenings are not recommended for those diagnosed via mammography with benign breast disease. Although the application of BI-RADS categories can vary with ability and experience level, the study authors acknowledged that at several screening centers, one radiologist interpreted the BI-RADS breast density and classification categories.