BACKGROUNDThe Norwegian Breast Cancer Screening Program started in 1996. To the authors' knowledge, this is the first report using individual-based data on invitation and participation to analyze breast cancer mortality among screened and nonscreened women in the program.MethodsInformation on dates of invitation, attendance, breast cancer diagnosis, emigration, death, and cause of death was linked by using unique 11-digit personal identification numbers assigned all inhabitants of Norway at birth or immigration. In total, 699,628 women ages 50 to 69 years without prior a diagnosis of breast cancer were invited to the program from 1996 to 2009 and were followed for breast cancer through 2009 and death through 2010. Incidence-based breast cancer mortality rate ratios (MRRs) were compared between the screened and nonscreened cohorts using a Poisson regression model. The MRRs were adjusted for calendar period, attained age, years since inclusion in the cohorts, and self-selection bias.RESULTSThe crude breast cancer mortality rate was 20.7 per 100,000 women-years for the screened cohort compared with 39.7 per 100,000 women-years for the nonscreened cohort, resulting in an MRR of 0.52 (95% confidence interval, 0.47-0.59). The mortality reduction associated with attendance in the program was 43% (MRR, 0.57; 95% confidence interval, 0.51-0.64) after adjusting for calendar period, attained age, years after inclusion in the cohort, and self-selection bias.CONCLUSIONSAfter 15 years of follow-up, a 43% reduction in mortality was observed among women who attended the national mammographic screening program in Norway.

DBT-supplemented screening resulted in significant increases in screen-detected cancers and specificity. However, no significant change was observed in the rate, size, node status, or grade of interval cancers. ClinicalTrials.gov: NCT01248546.

ammography screening reduces breast cancer mortality through early detection of small node-negative cancers (1,2). Digital mammography (DM) has two inherent limitations: low sensitivity in dense breasts because of a "masking effect" caused by overlying parenchyma and low specificity because summation of normal parenchyma can simulate a lesion. Results from retrospective studies (3-5) and prospective trials (6-8) have confirmed the potential of digital breast tomosynthesis (DBT) to address these limitations. Several studies implementing DBT in screening used "combo mode" DM + DBT (3-7). However, use of this mode results in a doubling of radiation dose. Synthetic mammography (SM) images are a potential solution to this challenge and require no additional radiation dose. The purpose of our prospective Oslo Tomosynthesis Screening Trial (OTST) was to compare diagnostic accuracy for independent reading of DM to DM + DBT, addition of computer-aided detection (CAD) to DM, and use of SM instead of DM in combination with DBT for breast cancer screening. Materials and Methods Hologic (Marlborough, Mass) sponsored this study by providing equipment and financial support for additional radiologist readings. Authors had full control of all data. The trial was approved by the regional ethical committee (clinical trial number NCT01248546). Written informed consent was required from all participants.

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Two-view digital breast tomosynthesis versus digital mammography in a population-based breast cancer screening program (To-Be): a randomized, controlled trialTomosynthesis breast in screeninga randomized controlled trial