OAK BROOK, Ill. - Researchers using automated breast density measurements have found that women with mammographically dense breast tissue have higher recall and biopsy rates and increased odds of screen-detected and interval breast cancer, according to a large new study from Norway published online in the journal Radiology. The study supports automated measurements as a future standard to ensure objective breast density classification for breast cancer screening, the researchers said.

Previous studies have shown that women with mammographically dense breasts face a higher risk of breast cancer and missed cancers than those with non-dense breasts, partly because the superimposition of dense breast tissue on mammograms leads to a masking effect, causing some cancers to go undetected. However, the majority of those studies relied on subjective density assessments -- most commonly, the radiologist's subjective interpretation using the American College of Radiology's Breast Imaging Reporting and Data System (BI-RADS). This approach introduces potential mammogram reader variability into density categorization, said the study's principal investigator, Solveig Hofvind, Ph.D., from the Cancer Registry of Norway in Oslo.

For the new study, Dr. Hofvind and colleagues used automated software to help classify mammographic density in 107,949 women ages 50 to 69 from BreastScreen Norway, a national program that offers women screening every two years. The researchers looked at a total of 307,015 digital screening examinations that took place from 2007 to 2015.
The automated software classified breasts as dense in 28 percent of the screening examinations. Rates of screen-detected cancer were 6.7 per 1,000 examinations for women with dense breast tissue and 5.5 for women with non-dense breasts. Interval breast cancer, or breast cancer detected between screenings -- usually by palpation -- was 2.8 per 1,000 in the dense breast tissue group and 1.2 for women with non-dense tissue.

The recall rate, or rate at which women are called back for additional examination based on suspicious mammographic findings, was 3.6 percent for women with dense breasts, compared with 2.7 percent in women with non-dense breasts. The biopsy rate of 1.4 percent in the dense breasts group was higher than the 1.1 percent rate for women in the non-dense category.

"The odds of screen-detected and interval breast cancer were substantially higher for women with mammographically dense versus fatty breasts in BreastScreen Norway," Dr. Hofvind said. "We also found substantially higher rates of recalls and biopsies among women with mammographically dense breast tissue."

Women's Health Homepage