Prospective Construction and Validation of a Prognostic Score to Identify Among Patients With Metastatic Breast Cancer Those Who Benefit From a Third Line Chemotherapy in Terms of Overall Survival

This is a biomedical study of interventional type. The trial will include 270 patients (180 patients in the first cohort and 90 patients in a second cohort) over a period of 3 years + 2 years of follow up. This prospective study will be conduct in patients who will receive a third line chemotherapy for metastatic breast cancer. The main objective of the study (first cohort) is to identify patients who benefit from a third line treatment in terms of overall survival with a score established from clinical, histological, but also biological "classic" and "innovative" (account of circulating tumor cells) criteria, all of these criteria must be measurable before the introduction of the 3rd line. This score will then be validated on the 2nd cohort. There will be no interruption of inclusions between first and second cohort of patients