Reduction of breast cancer mortality associated with mammography screening: a modelling study using population-based data from 2 French départements.

Meta-analyses of randomized controlled trials that started from 1963 to 1991 reported a decrease of breast cancer mortality associated with mammography screening. However, the effectiveness of population based screening programmes conducted nowadays may have changed, due to the better effectiveness of treatments for late stage cancers and the better diagnostic performance of mammography. The main objective of this study was to predict the reduction of breast cancer mortality associated with mammography screening in the French current setting. We compared breast cancer mortality in 2 simulated cohorts of women, which differed from each other solely by a 70% biennial participation in screening from 50 to 74 years old. The micro-simulation model used for predictions was calibrated with incidence rates of breast cancer by stage that were observed in Isere and Loire-Atlantique departements, France in 2007-2013. The model predicted a decrease of breast cancer mortality associated with mammography screening of 18% (95%CI: 5% - 31%) and 17% (95%CI: 3% - 29%), for models calibrated with data from Isere and Loire-Atlantique departements, respectively. Our results highlight the interest of biennial mammography screening from 50 to 74 years old to decrease breast cancer mortality in the current setting, despite improvement in treatment effectiveness.