Screening Outcomes Following Implementation of Digital Breast Tomosynthesis in a General-Population Screening Program

Screening mammography, despite ongoing controversy regarding its risk-benefit ratio, remains the mainstay of early breast cancer detection (1,2). Digital breast tomosynthesis (DBT), a relatively new x-ray technology (3,4) that images the breast in 3-D, has shown promise in addressing some limitations of conventional mammography by alleviating the effect of superimposed structures that can lead to erroneous interpretations (5–8). This new technology is increasingly implemented in breast clinics across the country, despite relatively little data on its clinical outcomes and effectiveness in specific patient populations (9). Early enthusiasm for DBT is based mostly on retrospective reader studies that compared DBT combined with digital mammography (DM) imaging vs DM alone. These studies demonstrated reductions of up to 30% to 40% in false-positives, with similar or slightly improved cancer detection (6,10–12). In the United States, Food and Drug Administration (FDA) approval was granted to a single vendor in 2011 (Hologic, Inc., Bedford, MA) based on a large multicenter retrospective reader study that demonstrated statistically significant improvement in performance when DBT was combined with DM (13,14). More recently, two prospective European trials have also shown improvements in screening outcomes with DBT. An interim analysis from the Oslo Screening Trial (n = 12631) and the final results from the Italian Screening with Tomosynthesis or Standard Mammography Trial (STORM, n = 7292) have demonstrated reductions in recalls of 15% to 17% and improvements in cancer detection of 33% to 53% (15,16). Furthermore, in the Oslo trial there was a 40% increase in the detection of invasive cancers with a stable rate of in situ cancer detection. However, in both of these trials subject compliance with screening invitations was less than 100%, and there were complex reading protocols requiring at least two readers per case, which is uncommon in clinical practices in the United States. More recently, two separate US centers have reported early results from DBT screening (17,18). These data again demonstrate improvements in outcomes with reductions in recalls up to 37% and increases in cancer detection up to 35%. At both sites, however, there was concurrent screening with DM alone and, therefore, a potential for bias in the selection of patients screened with DBT and potentially imaged with DBT at recall. In a recent report from a consortium of 13 US practices, a 15% reduction in recall rate and a 29% increase in cancer detection were seen with DBT screening compared with DM alone screening. However, no patient-level data was reported, and eleven of the thirteen sites had concurrent DM screening, leading to possible biases in selection of patients for DBT (19). Here we report the patient-level outcomes of implementing DBT screening for the entire screening population at our institution beginning October 2011. We compare outcomes for the cohort screened with DBT over a period of 17 months to the cohort screened with DM alone during the 12 months prior to DBT implementation. All women presenting for routine screening were imaged with DBT after its implementation, and radiologist readers remained the same over the DM and DBT cohorts, providing a “pre and post” comparison of DBT to DM-alone screening.