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.

Inclusion Criteria:

• Women with metastatic ductal adenocarcinoma breast cancer
• 18 years old or more
• Hormone receptors positive breast cancer (ER+ and/or PR+) on the last pathological analysis available.
• Acceptable patient's clinical situation compatible with chemotherapy or hormonotherapy administration
• PS <4
• Life expectancy > 3 months
• Evidence of measurable or evaluable disease (RECIST 1.1 criteria)in the 28 days before selection
• Information of the patient and signature of the informed consent form

Exclusion Criteria:

• Patient treated by chemotherapy or hormonotherapy for their metastatic disease (treatment failure under adjuvant hormonotherapy are accepted)
• Her2 positive breast cancer
• History of other stage II or III cancer in the 5 years. History of other metastatic cancer (whatever the time between the two cancers).
• Persons deprived of their freedom or under guardianship.
• Women unable to comply with the medical follow-up of the study for geographical, social or mental reasons.