In a recent study, researchers show that women with dense breast tissue have higher recall and biopsy rates and increased odds of screen-detected and interval breast cancer.
The new study from Norway is published 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 dense breasts face a higher risk of breast cancer and missed cancers than those with non-dense breasts.
This is partly because the superimposition of dense breast tissue on mammograms leads to a masking effect, causing some cancers to go undetected.
However, most studies relied on subjective density assessments—most commonly, the radiologist’s subjective interpretation.
This approach introduces potential mammogram reader variability into density categorization.
In the new study, the team used automated software to help classify 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% 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% for women with dense breasts, compared with 2.7% in women with non-dense breasts.
The biopsy rate of 1.4% in the dense breasts group was higher than the 1.1% rate for women in the non-dense category.
Mammographic sensitivity for detecting breast cancer was only 71% for women with dense breasts, compared to 82% for women with non-dense breasts.
Cancers detected at screening were more advanced among women in the dense breast tissue group.
Average tumor diameter for screen-detected cancers was 16.6 millimeters (mm) in the dense breasts group, compared to 15.1 mm for the non-dense group.
The results add another piece to the puzzle of screening protocols for women with dense breasts.
more than half of states in the U.S. have enacted breast density legislation, with some states requiring that women be informed about their breast density or that additional imaging could be beneficial.
However, supplemental screening for women with dense breasts currently is not recommended by any of the major health care societies or organizations, and more research is needed before widespread changes are made.
In the meantime, the researchers said that the findings will help inform how automated volumetric density categorization will change population-based screening performance and outcomes through a more objective breast density measurement method.
“The odds of screen-detected and interval breast cancer were substantially higher for women with dense versus fatty breasts.”
“We also found substantially higher rates of recalls and biopsies among women with mammographically dense breast tissue.”
“Breast density is here to stay, and it is in everyone’s best interest to embrace understanding and optimization of breast imaging practice to best address the needs of women with dense tissue.”
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