Breast Density Assessment Variation by Screening Modality
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 by Gastounioti et al in Radiology.
Density Assessment
A woman’s breast density 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 United States have passed legislation mandating that women be notified of their breast density, and a federal law was just recently passed requiring the U.S. Food and Drug Administration (FDA) to oversee such notification.
Although digital mammography has long been the foundation of breast cancer screening, new imaging or modalities are increasingly being used, including digital breast tomosynthesis (also known as three-dimensional [3D] mammography) and synthetic mammography. In 2011, the FDA approved the use of digital breast tomosynthesis in combination with digital mammography imaging. In 2015, the FDA approved the use of synthesized two-dimensional [2D] images, which are reconstructed from the digital breast tomosynthesis data set to replace digital mammography imaging, lowering the dose of digital breast tomosynthesis imaging.
Study Methods
In this retrospective study, researchers analyzed data from 24,736 women who underwent mammography screening at the Hospital of the University of Pennsylvania 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,” said Aimilia Gastounioti, PhD, lead author and research associate in the Radiology Department at the Perelman School of Medicine.
Results
Of the 60,766 imaging exams included in the study, 8,935 were conducted with digital mammography (14.7%); 30,799 (50.7%) were performed with digital mammography/digital breast tomosynthesis, and 21,052 (34.6%) used synthetic mammography/digital breast tomosynthesis. 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 digital mammography/digital breast tomosynthesis or synthetic mammography/digital breast tomosynthesis compared with digital mammography alone,” Dr. Gastounioti said. “These effects were more prominent among African American women and women with [a] higher BMI.”
Compared to standard digital mammography imaging, the odds of a high-density assessment were reduced by 31% and 57%, respectively, when mammographic imaging was performed with digital mammography/digital breast tomosynthesis or synthetic mammography/digital breast tomosynthesis. The odds of receiving a high breast density assignment after synthetic mammography replaced digital mammography were reduced by 38%.
The density downgrade may be due to the perception of less fibroglandular tissue in the 3D display of digital breast tomosynthesis imaging compared to digital mammography’s flat, 2D display, as well as differences in the appearance of the denser glandular tissue and the fatty tissue in the reconstructed synthetic mammography imaging.
“Our findings may have direct implications for personalized screening since breast density assignments, which often drive recommendations for supplemental screening, may vary greatly by modality, race, and BMI,” Dr. Gastounioti said.
She added that further research is needed to determine whether BI-RADS guidelines need to be adjusted for new imaging modalities.
Disclosure: The study authors’ full disclosures can be found at pubs.rsna.org.
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