The investigators propose in the present study an innovative approach, combining the most recent therapeutic opportunities in high risk ER+ breast cancer with the most recent and innovative diagnostic approaches such as the PAM50 signature and the RCB tumor response evaluation method. In line with the most recent recommendations on targeted anticancer therapies, the investigators have designed a parallel phase II randomized trial with early stopping rules 26, which will able in the meantime to build a unique prospective collection of tumor tissue, pre- and post-treatment.