Fewer women are assigned to a dense breast category when evaluated with advanced mammographic screening technologies compared to standard digital mammography, according to a new study published in the journal Radiology.
A woman’s breast density, or the relative amount of glandular and connective tissue compared to fatty tissue, is assessed during a breast cancer screening with mammography. Women with the highest level of breast density have an increased risk for breast cancer and are advised to discuss supplemental screening with their physician. Most states in the U.S. have passed legislation mandating that women be notified of their breast density, and a federal law was just recently passed requiring the U.S. FDA to oversee such notification.
Although digital mammography (DM) has long been the foundation of breast cancer screening, new imaging methods, or modalities, are increasingly being used, including digital breast tomosynthesis (DBT), also known as 3D mammography, and synthetic mammography (SM). In DM, two x-ray images are taken of the breast from top-to-bottom and from side-to-side while the breast is compressed against an imaging detector. In DBT, an x-ray tube moves in an arc over the compressed breast capturing multiple images from different angles. The DBT data can then be reconstructed into a quasi-3D image stack that allows better lesion characterization and localization.
In 2011, the FDA approved the use of DBT in combination with DM imaging. In 2015, the FDA approved the use of synthesized 2D images, which are reconstructed from the DBT data set to replace DM imaging, lowering the dose of DBT imaging.
In this retrospective study, researchers analyzed data from 24,736 women who underwent mammography screening at the Philadelphia-based Hospital of the University of Pennsylvania (HUP) between 2010 and 2017. Data collected included the breast density category assigned at the time of the screening using the standardized BI-RADS system, race, age and body mass index (BMI). The study population was 46% white and 54% African-American (mean age 56.3 years).
“Major strengths of our study were the size of our sample and the diverse patient population, which was approximately half white and half African-American,” says Aimilia Gastounioti, PhD, lead author and research associate in the radiology department at HUP’s Perelman School of Medicine. Of the 60,766 imaging exams included in the study, 8,935 were conducted with DM (14.7%), 30,799 (50.7 %) were performed with DM/DBT, and 21,052 (34.6 %) used SM/DBT.
A statistical analysis of the study data showed breast density assignments varied greatly by the screening method used. “We observed an overall trend of downgraded breast density when imaging was performed with either DM/DBT or SM/DBT compared with DM alone,” Gastounioti says. “These effects were more prominent among African-American women and women with higher BMI.”