Additional Screening May Not Be Necessary for Dense Breasts

Dense breast tissue should not be the sole determinant for supplemental or alternative screening methods following a normal mammogram, according to a study published in the Annals of Internal Medicine.

Researchers from California, Washington, New Hampshire, and Vermont undertook a study to determine which combinations of breast cancer risk and Breast Imaging Reporting and Data System (BI-RADS) breast density categories were associated with high interval cancer rates.

The researchers used screening data from the Breast Cancer Surveillance Consortium (BCSC) and reviewed 831,455 digital screening mammography examinations of 365,426 women aged 40 to 74 with no history of breast cancer, performed from January 2002 through October 2011.

The measurements included BI-RADS breast density, BCSC five-year breast cancer risk, and interval cancer rate (invasive cancer within 12 months after a normal mammography result) per 1,000 mammography examinations.

The results showed high interval cancer rates for women with five-year risk of 1.67% or greater and extremely dense breast tissue or five-year risk of 2.50% or greater with heterogeneously dense breast tissue (24% of all women with dense breasts).

The researchers also found that the interval rate of advanced-stage disease was highest (more than 0.4 cases per 1,000 examinations) among women with a five-year risk of 2.5% or greater and heterogeneously or extremely dense breasts (21% of all women with dense breasts).

The five-year risk was low to average for 51.0% of women with heterogeneously dense breasts and 52.5% of women with extremely dense breasts, with interval cancer rates of 0.58 to 0.63 and 0.72 to 0.89 case per 1,000 examinations, respectively.

The researchers concluded that digital mammography was effective in detecting breast cancer even in most women with dense breast tissue. “We found that not all women with dense breasts are at sufficiently high risk for interval cancer to justify consideration of supplemental or alternative screening methods,” they wrote. The need for alternative screening should be discussed between physicians and patients, taking into consideration the five-year breast cancer risk, not just breast tissue density.

An accompanying editorial reviewed the study’s findings, and the authors suggested that resources that are currently used to promote breast density notification legislation, which is in place in 22 states, would be more useful elsewhere: “Given the lack of scientific consensus, resources targeted for breast density legislation would be better devoted toward more accurate identification of women at high risk for interval breast cancer, research on optimal use of imaging methods, reduction of disparities in screening and early detection, and training of front-line primary care providers on breast cancer risk assessment.”