Effectiveness of Digital Breast Tomosynthesis Compared With Digital Mammography
Authors: Elizabeth S. McDonald, Andrew Oustimov, Susan P. Weinstein, Marie B. Synnestvedt, Mitchell Schnall, Emily F. Conant
Journal: JAMA Oncology (2016)

<h3>Importance</h3> Breast cancer screening with digital breast tomosynthesis (DBT) combined with digital mammography (DM) decreases false-positive examinations and increases cancer detection compared with screening with DM alone. However, the longitudinal performance of DBT screening is unknown. <h3>Objectives</h3> To determine whether the improved outcomes observed after initial implementation of DBT screening are sustainable over time at a population level and to evaluate the effect of more than 1 DBT screening at the individual level. <h3>Design, Setting, and Participants</h3> Retrospective analysis of screening mammography metrics was performed for all patients presenting for screening mammography in an urban, academic breast center during 4 consecutive years (DM, year 0; DBT, years, 1-3). The study was conducted from September 1, 2010, to September 30, 2014 (excluding September 2011, which was the transition period from DM to DBT), for a total of 44 468 screening events attributable to a total of 23 958 unique women. Differences in screening outcomes between each DBT year and the DM year, as well as between groups of women with only 1, 2, or 3 DBT screenings, were assessed, and the odds of recall adjusted for age, race/ethnicity, breast density, and prior mammograms were estimated. Data analysis was performed between February 16 and October 26, 2015. <h3>Exposure</h3> Digital mammography screening supplemented with DBT. <h3>Main Outcomes and Measures</h3> Recall rates, cancer cases per recalled patients, and biopsy and interval cancer rates were determined. <h3>Results</h3> Screening outcome metrics were evaluated for a total of 44 468 examinations attributable to 23 958 unique women (mean [SD] age, 56.8 [11.0] years) over a 4-year period: year 0 cohort (DM0), 10 728 women; year 1 cohort (DBT1), 11 007; year 2 cohort (DBT2), 11 157; and year 3 cohort (DBT3), 11 576. Recall rates rose slightly for years 1 to 3 of DBT (88, 90, and 92 per 1000 screened, respectively) but remained significantly reduced compared with the DM0 rate of 104 per 1000 screened. Reported as odds ratios (95% CIs), the findings were DM vs DBT1, 0.83 (0.76-0.91,<i>P</i> &lt; .001); DM vs DBT2, 0.85 (0.78-0.93,<i>P</i> &lt; .001); and DM vs DBT3, 0.87 (0.80-0.95,<i>P</i> = .003). The cancer cases per recalled patients continued to rise from DM0 rate of 4.4% to 6.2% (<i>P</i> = .06), 6.5% (<i>P</i> = .03), and 6.7% (<i>P</i> = .02) for years 1 to 3 of DBT, respectively. Outcomes assessed for the most recent screening for individual women undergoing only 1, 2, or 3 DBT screenings during the study period demonstrated decreasing recall rates of 130, 78, and 59 per 1000 screened, respectively (<i>P</i> &lt; .001). Interval cancer rates, determined using available follow-up data, decreased from 0.7 per 1000 women screened with the use of DM to 0.5 per 1000 screened with the use of DBT1. <h3>Conclusions and Relevance</h3> Digital breast tomosynthesis screening outcomes are sustainable, with significant recall reduction, increasing cancer cases per recalled patients, and a decline in interval cancers.