Daily Bulletin 2015

Breast Density Notification Laws Don't Affect Reporting Over Long-Term

Thursday, Dec. 03, 2015

Manisha Bahl, M.D., M.P.H

Manisha Bahl, M.D., M.P.H

Breast density notification laws have had an immediate but not long-term impact on the reporting of dense breasts on mammography, according to research presented Wednesday.

"Breast density notification laws and their attendant publicity have brought new attention to the assignment and importance of breast density," said the study's lead author Manisha Bahl, M.D., M.P.H, a breast imaging fellow at Duke University Medical Center. "Our results suggest that radiologists downgraded breast density assessment immediately after law enactment, but then resumed pre-law reporting patterns shortly thereafter."

Dr. Bahl said two possible explanations could account for the study results. Radiologists may have wished to simply avoid the new requirements for reporting, or they downgraded assessments out of fear that facilities would be overwhelmed by an increase in women seeking supplemental screening.

"Reporting practices may have been returned to pre-legislation levels once we realized the new requirements didn't pose significant burdens on individual- or facility-level workflow," Dr. Bahl said.

Although the topic is not without debate, breast density is considered to be important in two ways. First, dense tissue can mask abnormalities and therefore decrease the sensitivity of mammography for the detection of cancer. Second, the presence of dense tissue is an independent risk factor for the development of cancer.

The breast density notification laws are now in effect in 24 states, starting with Connecticut in 2009. But the laws lack consistency from state to state. Dr. Bahl said some require only notification to patients that their breasts are dense, while others specify supplemental screening must be offered. Only four states (Illinois, Indiana, Connecticut and New Jersey) mandate insurance coverage of supplemental screening.

The study accessed the National Mammography Database, which includes data from 4 million mammograms over a five-year period (2010 to 2014).

The results showed a statistically significant decrease in the percentage of mammograms reported as dense in the month after enactment of the law compared to the month before. Thus, the legislation appears to have been the catalyst for the decrease.

Within 10 months the percentage of mammograms reported as dense returned to their pre-legislation levels.

Other possible factors for the fluctuation include the 2013 release of the Breast Imaging Reporting and Data System (BI-RADS) Fifth Edition and/or the introduction of tomosynthesis.

"BI-RADS Fifth Edition eliminated numerical ranges of percentage dense tissue for the four density categories in an effort to emphasize that the subjective assessment of breast density is a more useful indicator of cancer risk than percentage density," Dr. Bahl said.

However, Dr. Bahl said it is more likely the fluctuations came in direct response to the legislation because the fluctuations did not occur in states without the law during the same period.

Breast density on mammography is classified by the radiologist's subjective assessment into one of four categories: almost entirely fatty, scattered areas of fibroglandular density, heterogeneously dense, and extremely dense.

Trends in the percentage of mammograms reported as heterogeneously dense or extremely dense, beginning ten months before and continuing ten months after enactment of breast density notification laws. There was a statistically significant decrease in the percentage of mammograms reported as dense in the month after law enactment compared to the month before (arrows).

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The RSNA 2015 Daily Bulletin is owned and published by the Radiological Society of North America, Inc., 820 Jorie Blvd., Oak Brook, IL 60523.