In France, to promote the quality of cancer care, decisions have currently to be made according to clinical practice guidelines (CPGs) during regularly organized multidisciplinary staff meetings (MSMs). Dissemination of textual CPGs has a poor impact on clinical practice as opposed to the use of clinical decision support systems (CDSSs) known to improve compliance with CPGs. OncoDoc2 is a CDSS providing patient-specific recommendations based on CPGs for non-metastatic female breast cancer management elaborated by the CancerEst INTERMEDICAL collaboration.The main goal of the study is to evaluate the effect of the routine use of OncoDoc2 during MSMs on compliance of MSM decisions with local CPGs. Impact will be measured by the compliance rate of MSM decisions with OncoDoc2 recommendations. The design of the study relies on a cluster randomized controlled trial. Under the assumption of a baseline compliance rate of 70% without intervention, an expected compliance rate of 90% in the intervention group (α = 5%, β = 20%), an inter-cluster variability of 5%, and 59 decisions per center, the required number of centers is 3 in each group, or 177 decisions in each arm. The study will be conducted in cancer care centers (public and private) from Paris area, France.This prospective trial will be conducted in two steps. First, baseline compliance rates will be measured in each center. Then, the 6 centers will be randomized into 2 arms. In the intervention arm, OncoDoc2 will be used during MSMs at decision time. Every case of non-adherence with system recommendations will have to be justified by clinicians. In both arms and after each MSM, MSM decisions will be recorded as well as patient characteristics and OncoDoc2 will be used for each patient case to get system recommendations. In the intervention arm, OncoDoc2 recommendations obtained by MSM will also be recorded, as well as the reason for non following recommendations in case MSM decision does not comply with guidelines.