Study of ESR1 Mutations in Metastatic Breast Cancer

Breast cancer is the most common cancer in woman. Aromatase inhibitors have demonstrated a real efficacy however a resistance to treatment exists. ESR1 mutations appear like involved in the mechanism of resistance to aromatase inhibitors treatment. The purpose of the study is to determine the frequency ESR1 mutations by Digital PCR in patient with metastatic breast cancer. The significance of the Digital PCR technique will be determined first in plasma issued from healthy volunteers. At the initiation of aromatase inhibitors treatment patient with metastatic breast cancer will be included in the study. During their follow-up visit every 3 months), their status towards their disease will be collected and a plasma will be collected too. When the patient progress clinically or radiologically the plasma concomitant to this progression will be analysed by Digital PCR to detect ESR1 mutations. The patient will be followed during 2 years.