Breast cancer represents the female cancer with the highest incidence. The cure rate is very high thanks to the possibility of applying very active drugs at an early stage; but a part of the patients undergoes metastasization and needs therapies to control the advanced stage of the disease. Among the newest drugs, CDK 4/6 inhibitors have particular relevance for HR+/HER2- breast cancer. These latest generation inhibitors have demonstrated their important antitumor activity in several randomized phase III clinical trials conducted in metastatic breast cancer. The use of these new therapeutic resources (also in relation to costs, toxicity profiles and patient preferences) will be the main object of the program, starting from practical clinical situations.