Breast Density Classification on Mammography Often Inconsistent
Breast density assessments can vary for as many as 19% of women, which can lead to inconsistent information regarding the need for additional clinical screenings, according to a systematic review recently published in the Annals of Internal Medicine (doi:10.7326/M15-1789).
Mammographic sensitivity is decreased for women with dense breasts, while at the same time, dense breasts are associated with an increased risk of breast cancer. So, women with dense breasts are often urged to seek supplemental screening.
In a review of 24 studies, researchers analyzed the reproducibility of breast density determinations. The review was supported by the Agency for Healthcare Research and Quality, an agency within the US Department of Health and Human Services.
"The number of states mandating that breast density information be reported to patients is increasing," said Joy Melnikow, director of the Center for Healthcare Policy and Research at University of California (UC) Davis, and first author on the paper. "But the assignment of breast density is not terribly consistent. The policy may be out in front of the science."
The Breast Imaging Reporting and Data System (BI-RADS) uses 4 categories to define breast density: A, mostly fatty; B, scattered density; C, consistent density; and D, extremely dense. Women classified with dense breasts (categories C and D) may be offered supplemental screening with ultrasound or magnetic resonance imaging (MRI). However, this study shows that approach may not be supported by strong scientific evidence.
This review found that women's breasts were reclassified over several years of sequential screening, possibly leading to confusion or lowered confidence in the screening results. After consecutive mammographies, as many as 22% of women's breasts were reclassified from dense to nondense (or vice versa). Changing density classification would then change clinical recommendations for supplemental screening.
"It is important to be clear who actually has dense breasts," said Melnikow. "Also, when patients are told their breasts are either dense or not dense, they need to have confidence in that assessment."
The best solution for patients is to conduct long-term, rigorous research to better standardize breast density classification and determine whether supplemental screenings provide actual health benefits for women, explained Melnikow.