The STIC CTC study is a randomized trial to evaluate the medico-economic interest of taking into account circulating tumor cells (CTC) to determine the kind of first line treatment for metastatic, hormone-receptors positive, breast cancers. In the standard arm, the kind of treatment will be decided by clinicians, taking into account the criteria usually used in this setting. In the CTC arm, the type of treatment will be decided by CTC count: hormone-therapy if <5CTC/7.5mll (CellSearch technique) or chemotherapy if =5. The main medical objective is to demonstrate the non-inferiority of the CTC-based strategy for the progression-free survival: 994 patients are needed, and will be accrued in French cancer centers. Secondary clinical objectives are to compare toxicity, quality of life and overall survival between the two arms. The medico-economic study will compare cost per progression-free life years gained of the two strategies. The financial impact of centralized (one platform) vs decentralized (several platforms) CTC testing will be evaluated.