The primary objective of the study is to evaluate whether digital breast tomosynthesis plus synthesized 2D mammograms leads to a relevant increase in the detection rate of screening-detected invasive cancers compared to 2D full-field digital mammography in routine screening according to the European Guidelines. Furthermore, the incidence rate of interval cancers within a 24 months interval after screening will be compared between both study arms in order to investigate the potential for overdiagnosis.
According to the pre-defined order of both primary endpoints and the primary objective of the study in the planning phase, the initial sample size calculation was based solely on the first primary endpoint (invasive breast cancer detection rate). Given the increasing national and international attention of interval cancers to assess the impact of potential overdiagnosis caused by tomosynthesis, we have planned a sample size increase from 80,000 to 120,000 study participants to achieve a reasonable statistical power for the evaluation of both primary endpoints. The revised sample size calculation was carried out without knowledge of the data from the currently recruiting TOSYMA study, i.e. all planning assumptions were based on external data that do not belong to the ongoing study.
