Impact of Breast Density Notification Legislation on Radiologists' Practices of Reporting Breast Density: A Multi-State Study

Purpose: To evaluate the impact of breast density notification legislation on breast density reporting by radiologists nationally. Materials and Methods: The institutional review board exempted this HIPAA-compliant retrospective study from the requirement for informed consent. State-level data over a 5-year period on breast density categorization and breast cancer detection rate were collected from the National Mammography Database (NMD). Z tests were used to calculate differences in proportions. Results: Facilities in 13 of 17 states that had breast density notification legislation as of 2014 submitted data to the NMD before and after law enactment. A total of 1 333 541 mammographic studies (hereafter called "mammograms") over a 30-month period, beginning 20 months before and continuing 10 months after law enactment, were included in the analysis. There was a small but statistically significant decrease in the percentage of mammograms reported as showing dense breast tissue (hereafter called "dense mammograms") in the month before law enactment compared with the month after (43.0% [22 338 of 52 000] vs 40.0% [18 604 of 46 464], P < .001). There was no statistically significant difference in the percentage of mammograms reported as dense in the month before law enactment compared with the 10th month after (43.0% [22 338 of 52 000] vs 42.8% [15 835 of 36 991], P = .65). There were no significant differences in the breast cancer detection rate between the month before and the month after law enactment (3.9 vs 3.8 cancers per 1000 mammograms, P = .79) or between the month before law enactment and the 10th month after (3.9 vs 4.2 cancers per 1000 mammograms, P = .55). In 21 analyzed states without breast density notification legislation, the percentage of mammograms reported as dense did not decrease below 42.8% (43 363 of 101 394) from 2010 to 2014, in contrast to 13 analyzed states with breast density notification legislation, which reached a nadir of 39.3% (20 965 of 53 360) (P < .001). Conclusion: The percentage of mammograms reported as dense slightly decreased immediately after enactment of breast density notification legislation but then returned to prelegislation percentages within 10 months. (C) RSNA, 2016