In France, a pilot program for organized breast cancer screening began in 1989 and was gradually expanded to all departments. The primary goal of systematic breast cancer screening is to reduce mortality associated with this cancer. A collaborative working group, bringing together representatives from cancer registries, screening management organizations, and cancer centers and led by the InVS, was formed to conduct a quantitative assessment of the impact of organized screening on breast cancer mortality in France. The prevalence of individual screening in France and its coexistence with organized screening led the working group to consider both types of screening practices. This interim report presents a literature review of methods for estimating the impact of screening on mortality, the methods considered in the French context, as well as a synthesis of the various available data sources and French studies concerning mammography practice, tumor characteristics, and survival. The methodology, based on modeling disease progression coupled with a survival analysis, taking into account tumor prognostic factors, appeared to be the most robust in the French context. This approach allows for estimating the effect of a screening strategy compared to a situation without screening, in terms of reducing breast cancer mortality. The disease progression model (Markov model) allows for the prediction of the distribution of tumor characteristics in each scenario. The parameters of this model are estimated using data from screening management systems. Survival analysis translates the difference in distribution between the two scenarios into a reduction in mortality. This methodology is currently being implemented, and the results obtained will be the subject of a future report.