Inclusion Criteria:

          -  Post-menopausal women or women receiving Luteinizing hormone-releasing hormone (LHRH)
             analogs

          -  Histologically confirmed metastatic breast cancer RH+

          -  Measurable metastatic breast cancer (modified RECIST criteria) or not measurable but
             evaluable

          -  Recurrence:

               -  being treated with aromatase inhibitors (AIs)

               -  after adjuvant treatment by AIs

               -  after progression of the metastatic cancer in patients receiving AIs following
                  positive response during at least 6 months

          -  Performance status ≤ 2

          -  Haematological test: polynuclear neutrophiles ≥ 1.5 × 109 /L, haemoglobin ≥ 9 g/dL,
             blood platelet ≥ 100 × 109 /L

          -  Hepatic function: albumin ≥ 2.5 g/dL, serum bilirubin ≤ 1.5 × N (except if Gilbert's
             Syndrome) , aminotransferases ≤ 3 × N (≤ 5 × N if hepatic metastases)

          -  Renal function: serum creatinine ≤ 1.5 mg/dL or clearance of creatinine ≥ 40 ml/min

          -  Women without endometrial pathology

          -  Ability to provide written informed consent before the start of any study specific
             procedures

        Exclusion Criteria:

          -  Age < 18 years old

          -  Pre-menopausal, pregnant or pregnant or breast feeding females

          -  Patient who should exclusively be treated by chemotherapy

          -  Women previously treated with chemotherapy but not by AIs

          -  Women previously treated by tamoxifen for their metastatic breast cancer

          -  HER2+

          -  Concurrent anti-cancer treatment (chemotherapy, surgery, immunotherapy, biological
             therapy and tumour embolism)

          -  Concurrent treatment with protocol-defined prohibited medications

          -  Malabsorption syndrome , significant digestive dysfunction, gastrectomy, jejunectomy,
             hemorrhagic recto colon

          -  Concurrent disease or condition that may interfere with study participation, or any
             serious medical disorder that would interfere with the subject's safety (for example,
             active or uncontrolled infection or any psychiatric condition prohibiting
             understanding or rendering of informed consent)

          -  Any pathology, including severe psychiatric or psychologic disease that may harm
             patient's safety or participation in the study

          -  Serious or not cured or unstable toxicity due to the administration of another drug
             being involved in clinical trials

          -  Uncontrolled cardiovascular pathologies

          -  Previous history of thromboembolic event like deep vein thrombosis or pulmonary
             embolism recorded within one year before the inclusion date

          -  Active uncontrolled infection

          -  Existence of an increased risk of thromboembolic event, apart from the metastatic
             cancer condition, such as:

               -  known presence of antiphospholipid antibody

               -  family history of thrombophilia

               -  existence of any clinical, genetic, or biological abnormality which can increase
                  the risk of thromboembolic event according to the

          -  Participation to a clinical trial at least 4 weeks prior the start of the study