The Digital Breast Tomosynthesis Trial in Bergen

DBT is a new screening tool, argued to be better than standard DM. This statement is based on a lower recall rate, and a higher rate of early-stage screen-detected cancer. No studies have so far reported results from women screened with DBT from GE Healthcare, as far as the investigators know. DBT from GE offer synthetic two-dimensional DM generated from the DBT data (SM), and studies have shown similar detection rates for this technique as of adjacent DM. By comparing results of early performance measures and economic aspects in two comparable populations of women in the same age group, residing in the same county, the investigators can measure the effect of SM+DBT versus standard DM with equipment from GE Healthcare. The populations will be examined by the same radiographers, screen-read by the same radiologists, histologically breast cancer proven by the same pathologists, and treated by the same surgeons and oncologists. A prospective cohort study targeting 45,000 women invited to breast cancer screening in Bergen, Hordaland in the study period, 2016-2018, will be performed. A screening participation of approximately 75% is expected. All attending women will be asked if they are willing to participate in the study after receiving written and oral information about the study. Women willing to participate in the study will sign an informed consent. Of the attending women it is expected that about 90-95% will consent to participate in the study. The women will be randomized into two groups, a study group and a control group. The randomization will take place at the screening unit in Bergen. The outcome of the randomization is based on the 11-digit personal identification number assigned to every citizen in Norway. In the study group, the women will be screened with SM+DBT. In the control group, the women will be screened with DM. Women not willing to participate in the study will be screened with DM, and not included in our study. The investigators aim to address the following topics and research questions: * Study 1: Early performance measures in a population based screening program using SM+DBT versus DM - interim analyses. * Study 2: Use of SM+DBT versus DM in a population based screening program - a randomized controlled trial. * Study 3: Prognostic and predictive histopathologic characteristics of breast tumors detected in a population based program using SM+DBT versus DM. * Study 4: SM+DBT and DM in a populations based screening program - which technology has the highest sensitivity for women with mammographic dense breast? * Study 5 and 6: Costs of SM+DBT and DM in a populations based screening program - is SM+DBT cost-effective?