Digital breast tomosynthesis (DBT) improved breast cancer screening performance in community practice and identified more invasive cancers, compared to digital mammography, according to new research from a U.S. consortium. Radiologists’ interpretive performance also improved with DBT.
“As facilities replace older equipment, DBT units will become the norm,” lead author Christoph I. Lee, M.D., told Inside Precision Medicine. He is director of the Northwest Screening and Cancer Outcomes Research Enterprise at University of Washington.
The results of the study were published this week in Radiology.
“Our study demonstrated that more radiologists in U.S. community practice are meeting recommended performance standards with digital breast tomosynthesis than they did with digital mammography,” said Lee. “This is good news for women and breast cancer screening, as digital breast tomosynthesis has quickly become the most popular breast cancer screening modality in the U.S.”
Lee said, “Tomosynthesis acquires multiple slices through the breast rather than just 2D projections as is the case of digital mammography. It allows evaluation of overlapping tissue and potentially increases detection of small cancers.”
Routine mammography screening is recommended for women at average risk of breast cancer by all major policy bodies, including the United States Preventive Services Task Force and American Cancer Society. Since the 1960s, mammographic imaging technology has transitioned from screen-film mammography, to digital mammography, and finally digital breast tomosynthesis (DBT), which was approved in 2011 and is now available in 84% of all mammography screening facilities in the U.S.
“Data from the FDA over time shows DBT units eclipsing digital mammography units,” said Lee. Further, he said, the addition of DBT is relatively easy for doctors. “The FDA only requires 8 hours of DBT training for radiologists who interpret digital mammography. This is because the DBT image slices are similar to digital mammography.”
Breast cancer mortality reduction from routine screening relies not just upon modality, but upon radiologists’ interpretive performance. Since the Mammography Quality Standards Act was enacted in 1992, screening facilities and interpreting radiologists have been required to meet minimum quality standards.
The Breast Cancer Surveillance Consortium (BCSC) has published screening performance benchmarks since 2006. The BCSC is a collaborative network of U.S. breast imaging registries conducting research to assess and improve the delivery and quality of breast cancer screening and related patient outcomes.
To establish performance benchmarks for DBT screening and evaluate performance trends over time in U.S. community practices, this research team collected DBT screening exams from five BCSC registries between 2011 and 2018.
Performance measures included abnormal interpretation rate, cancer detection rate, sensitivity, specificity and false-negative rate.
Compared to BCSC digital mammography screening exams from the same time period and previously published BCSC and National Mammography Database performance benchmarks, all performance measures were higher for DBT except sensitivity and false-negative rate, which were similar to concurrent and prior digital mammography performance measures.
“Radiologists appear to perform better with digital breast tomosynthesis and have higher accuracy on screening 3D mammograms than 2D mammograms across U.S. practices,” Lee noted. “As this becomes the mainstay screening modality, we hope to see improved screening outcomes for women.”
This retrospective study included 896,101 women who underwent 2,301,766 screening exams—458,175 DBT and 1,843,591 2D digital mammography. The abnormal interpretation rate for DBT was 8.3%, cancer detection rate was 5.8 per 1,000 exams, sensitivity was 87.4%, and specificity was 92.2%.
With DBT, 97.6%, 91.8%, 75.0%, and 74.0% of assessed radiologists achieved the recommended acceptable performance ranges for cancer detection rate, sensitivity, abnormal interpretation rate and specificity, respectively.