Breast Cancer Surveillance Consortium Analysis of Trends in Breast Density Assessment


Key Points

  • No significant difference in prevalence of dense breasts was observed between the BI-RADS 4th edition (2005–2013) and 5th edition (2014–2016) eras.
  • No significant difference in prevalence was observed between digital breast tomosynthesis screens and digital mammography screens in the BI-RADS 5th edition era.

In a study reported in the Journal of the National Cancer Institute, Sprague et al found that only small changes in the proportions of women found to have dense breasts on digital mammography have occurred with revisions in Breast Imaging Reporting and Data System (BI-RADS) density classification guidelines and an increased use of digital breast tomosynthesis.

The study involved data from 2,990,291 digital mammography screens and 221,063 digital breast tomosynthesis screens interpreted by 722 radiologists from 144 facilities in the Breast Cancer Surveillance Consortium.

Prevalence of Dense Breasts

From 2005 through 2016, density category distributions on digital mammography screens were 9.5% to 10.3% for almost entirely fat, 41.5% to 44.7% for scattered densities, 38.3% to 40.8% for heterogeneously dense, and 6.5% to 8.3% for extremely dense.

In an analysis using age standardization, 46.3% of digital mammography screens were assessed as dense (heterogeneously/extremely dense) during the BI-RADS 4th edition era (2005–2013), compared with 46.5% during the BI-RADS 5th edition era (2014–2016; P = .93). Among digital breast tomosynthesis screens in the BI-RADS 5th edition era, 45.8% were assessed as dense (P =.77 vs 46.5% assessed as dense by digital mammography in the BI-RADS 5th edition era). Similar results were obtained in analyses of all four density categories and different age subgroups.

The investigators concluded, “[O]ur results suggest that, across screened populations, clinicians and researchers may reasonably expect breast density assessments made since 2014 to be comparable to those recorded previously. Health-care providers and policymakers should expect the prevalence of dense breasts to remain stable despite changes in the BI-RADS lexicon and the dissemination of digital breast tomosynthesis.”

B.L. Sprague, PhD, of the Departments of Surgery and Radiology, University of Vermont Cancer Center, University of Vermont, Burlington, is the corresponding author for the Journal of the National Cancer Institute article.

Disclosure: The study was supported by the National Cancer Institute. The study authors’ full disclosures can be found at

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.