Previous research has shown that DBT has a higher sensitivity for breast cancer detection than digital mammography
Screening with digital breast tomosynthesis (DBT) reduces the rate of interval breast cancers compared to screening with digital mammography, according to a study published in Radiology. The study adds to a growing body of evidence supporting DBT as a breast cancer screening tool with important advantages over mammography.
DBT works by capturing a series of X-ray images of the breast from different angles. Previous research has shown that it has a higher sensitivity for breast cancer detection than digital mammography.
The impact of these additional DBT-detected cancers is not fully understood. While they may constitute a screening benefit, they could also contribute to overdiagnosis, a term for the diagnosis of early-stage, slow-growing cancers that would not have caused harm to the patient in their lifetime.
The rate of interval cancers—cancers that arise between routine screenings—offers one way to better elucidate screening benefits. They are considered more aggressive than cancers detected during a screening exam.
“Interval cancers have, in general, a more aggressive biological profile than screen-detected cancers,” said study lead author Kristin Johnson, M.D., radiology resident at Skåne University Hospital in Malmö, and Ph.D. student at Lund University, Sweden. “This means that the prognosis is less favourable for interval cancers compared to screen-detected cancers.”
Interval cancer detection rate reporting is required in many screening programs as an indicator of effectiveness. A reduction in the interval cancer rate when using DBT might be attributed to improved detection of rapidly growing cancers with poorer prognosis, possibly contributing to lower breast cancer mortality.
For the new study, Dr Johnson and colleagues compared interval cancer rates in Sweden’s population-based Malmö Breast Tomosynthesis Screening Trial with those from an age-matched control group of patients who underwent digital mammography at the same center.
The study group included almost 15,000 women who were screened with DBT and digital mammography between 2010 and 2015. Those women were matched with a control group of more than 26,000 women who had only digital mammography screening during the same time period.
The interval cancer rate in the patients screened with DBT and digital mammography was 1.6 per 1,000 screened, significantly lower than 2.8 per 1000 in the group screened with digital mammography only. The interval cancers in the trial generally had non-favourable characteristics.
The reduced interval cancer rate after screening with DBT could translate into screening benefits, according to Dr Johnson.
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