DBT still superior to mammography after 5-year follow-up

Digital breast tomosynthesis has been shown to detect more cancers with fewer false positives, but new research proves those benefits hold true even after multiple years and rounds of cancer screening.

University of Pennsylvania researchers analyzed thousands of breast cancer exams performed over a five-year period to complete their study, published March 10 in Radiology. It’s one of the longest study periods comparing DBT to traditional mammography that’s been published to date, said lead author Emily F. Conant, MD.

"We showed that the improved performance with DBT was maintained over multiple years," Conant, chief of breast imaging at Penn’s School of Medicine, added in a statement. "This is the longest follow-up with cancer registry matching that has been published thus far."

There have been a number of studies showing DBT’s superiority over digital mammography at detecting cancers and reducing the number of women called back for imaging due to suspicious findings, but most have only covered initial rounds of screening. During that time frame, detection and recall rates are expected to be higher than later screening rounds.

In order to get a better sense of how DBT performs over longer stretches, Conant and colleagues examined patient outcomes from more than 56,000 DBT exams and 10,500 digital mammography cases. They compared imaging findings with local cancer registry results.

Overall, digital tomosynthesis detected 6 cancers per 1,000 women screened, compared to mammography’s rate of 5.1 cancers per 1,000 cases. The former also achieved a better recall rate (8% vs. 10.4%).

DBT, which also identified more potentially harmful cancers than digital mammography, offers radiologists a clearer picture of benign and malignant lesions. This fact, Conant said, may be partially responsible for the improved outcomes seen in women screened with DBT.

"With tomosynthesis you can remove some of the overlapping or obscuring breast tissue so that both normal and abnormal findings are better seen," she said. "That provides both improved cancer detection and decreased false positives."

Conant also highlighted the diversity of women included in their analysis as a “key strength” of the study. Black women, for example, are considered more at risk for developing aggressive cancers, and made up nearly half of the study cohort.

"We found different types of biology in the cancers detected across our diverse population and that's an important takeaway of this paper," Conant said. "Our results show that we can improve our screening outcomes for younger women with DBT by finding clinically important cancers earlier with fewer false positives."