High Variability in Diagnosis of Dense Breasts

When examining mammograms, radiologists can differ widely in their interpretation of whether a woman has dense breasts, according to a new study published in Annals of Internal Medicine.

“There is wide variation in density assessment across radiologists that should be carefully considered by providers and policymakers when considering supplemental screening strategies,” wrote study author William E. Barlow, PhD, professor of statistics at the University of Washington School of Public Health, and colleagues. “The likelihood of a woman being told she has dense breasts varies substantially according to which radiologist interprets her mammogram.”

The multicenter observational study compiled data from 83 radiologists, each of whom interpreted at least 500 screening mammograms between 2011 and 2013. The analysis included 216,783 mammograms from over 145,000 women.

Overall the study found that 36.9% of mammograms were from patients with dense breasts, but this rate varied widely across radiologists, from 6.3% to 84.5%. The variation among clinicians in judging breast density was similar regardless of other patient characteristics.

Among women who had multiple mammograms evaluated by different radiologists, 17.2% had disagreeing results, sometimes receiving a dense breast status and sometimes not.

The variability found in this analysis has implications for supplemental screening for women evaluated as having dense breast tissue, according to the authors. Currently, half of the states in the United States have legislation that dictates that women must be told about their breast density status and that additional screening tests should be considered if they have dense breasts.

The issue with such legislature is that the evaluation of breast tissue density using mammography is subjective.

Recently the American College of Radiology released a statement that highlighted the lack of reproducibility in the evaluation of women’s breast density and expressed caution regarding the potential unintended harms that mandatory breast density notification could cause patients.

The results of this study are further evidence that eliminating the subjectivity of breast density evaluation is needed by developing objective and standardized ways to measure the density of breast tissue, the authors noted. Ways to make these evaluations objective include both better training of radiologists and implementing automated density quantification tools.