Increased detection of relevant breast cancers with DBT in mammography screening?

Abstract Screening with digital breast tomosynthesis plus synthetic mammography (DBT+SM) increases invasive breast cancer detection compared to digital mammography (DM). Since a reduction in breast cancer mortality is largely based on the detection of histological grade 2 or 3 breast cancers, a comparison of the detection rates of invasive breast cancers (iCDR), independent of the stage, of grades 2 or 3, was carried out, taking into account breast density, after screening with DBT+SM vs. DM. The 1:1 randomized, multicenter TOSYMA study recruited participants from 7/2018 to 12/2020 in the German Mammography Screening Program. This explorative subanalysis included 49479 participants in the DBT+SM arm and 49689 participants in the DM arm, with complete documentation including visual density categorization (A/B: non-dense parenchyma, C/D: dense parenchyma). The iCDR of grade 2 or 3 was 5.1 per 1000 women screened with DBT+SM vs. 3.6 ‰ screened with DM (difference +1.5 ‰). In the case of non-dense parenchyma, the corresponding DBT+SM rate was 4.5 ‰ (difference to DM +1.3 ‰), and in dense parenchyma it was 5.7 ‰ (difference to DM +1.7 ‰). The iCDR of grade 1 was 2.1 ‰ with DBT+SM (difference to DM +0.8 ‰). In non-dense parenchyma, the corresponding DBT+SM rate was 1.7 ‰ (difference to DM +0.7 ‰), in dense parenchyma it was 2.6 ‰ (difference to DM +1.0 ‰). When screening with DBT+SM, invasive breast cancer detection rates of grade 2 or 3 tumors are higher than with DM. Detection rates and their differences are also higher in women with dense than non-dense parenchyma. These detection rates and their differences are consistently higher for DBT+SM and DM than those for grade 1 cancers. The explorative analyses of this large, randomized trial indicate that DBT+SM screening increases the detection of prognostically more relevant breast cancers.