"Dense breasts" diagnosis varies widely among radiologists

The likelihood of a woman being told she has dense breasts varies substantially according to which radiologist interprets her mammogram. These findings, published in Annals of Internal Medicine, have policy implications with regard to supplemental screening strategies.

Having dense breasts makes it more difficult to interpret mammography results and is also an independent risk factor for developing breast cancer. To ensure that women with dense breasts are aware of the limitations of mammography and their increased risk for cancer, about half of U.S. states currently have breast density notification laws and some of those states require that women are advised to talk to their health care providers about supplemental screening. Such laws are controversial because of the large number of women affected and because the lack of consensus in the medical community regarding supplemental screening strategies. An additional concern is the subjective nature of breast density assessment, which is based on the Breast Imaging Reporting and Data System (BI-RADS) that provides four possible categories for breast density.

Using data from 30 radiology facilities within the three breast cancer screening research centers of the Population-based Research Optimizing Screening through Personalized Regimens (PROSPR) consortium, researchers sought to examine variations in the distribution of breast density assessment across radiologists as recorded in clinical practice. They also accounted for factors known to be associated with breast density. The researchers found a wide variation among radiologists in the percentage of mammograms rated as showing dense breasts (ranging from 6.3 percent to 84.5 percent), which persisted after adjustment for patient factors. In addition, more than 1 in 6 women with consecutive mammograms interpreted by different radiologists during a short period were reclassified into dense versus nondense categories. According to the researchers, this variation has important implications for debates about mandatory notification laws.