Assessment of screen-recalled abnormalities for digital breast tomosynthesis versus digital mammography screening in the BreastScreen Maroondah trial

Introduction Australia's first population-based pilot trial comparing digital breast tomosynthesis (DBT) and digital mammography (DM) screening reported detection measures in 2019. This study describes the trial's secondary outcomes pertaining to the assessment process in women screened with DBT or DM, including the type of recalled abnormalities and the procedures performed. Methods Women with suspected abnormalities at screening were recalled for further investigation. Outcome measures were number of lesions assessed, types of imaging findings recalled to assessment, and data on testing and assessment outcomes; these were reported using descriptive analyses of lesion-specific data. Results A total of 274 lesions and 203 lesions were reported in the DBT-screened and DM-screened groups, respectively. There were a higher proportion of lesions depicted as calcifications (32.4% vs 21.3%), and a lower proportion of lesions depicted as asymmetrical densities (3.2% vs 15.7%) for DBT recalls than DM recalls. A lower proportion of DBT-recalled lesions was assessed with additional mammography than DM-recalled lesions (49.3% vs 93.1%). Higher proportions of DBT-recalled lesions than DM-recalled lesions were investigated with clinical breast examination (50.4% vs 39.9%), core needle biopsy (45.6% vs 28.6%) and open biopsy (4.0% vs 1.0%). Similar proportions of DBT- and DM-recalled lesions were assessed using ultrasound (76.3% vs 71.4%). Conclusion Assessment of screen-recalled lesions showed that, compared with DM, DBT found more benign and more malignant lesions, and generally required more procedures except for less additional mammography workup. These findings show that a transition to DBT screening changes the assessment workload.