Prognostic Impact of the Neutrophil/Lymphocyte Ratio (NLR) in the Treatment of First-line Metastatic or Locally Advanced Breast Cancer Treated With CDK4/6 Inhibitor.

Inclusion Criteria: * Patients with locally advanced or metastatic HR-positive, Her2-negative breast cancer * Patients who are scheduled to receive first-line metastatic CDK4/6 inhibitor therapy in combination with hormone therapy as per the marketing authorization * Patients who have not received previous anti-neoplastic therapies for metastatic or advanced disease (chemotherapy, targeted therapy or hormonal therapy). However, it will be possible to have initiated 1st line hormonal therapy within 4 to 6 weeks prior to inclusion. * Prior radiotherapy allowed even in metastatic disease. In case of radiotherapy treatment, side effects attributable to the treatment must be resolved. * Postmenopausal patients or patients with suppressed ovarian function * Patient with measurable or non-measurable disease (according to RECIST v1.1 criteria) * Adequate organ and marrow function to allow prescription of CDK 4/6 inhibitor therapy * Age of Patient ≥ 18 years * Willingness and ability to comply with scheduled visits, treatment plan, biologic tests and other trial procedures including assessments requested for inclusion * Patient affiliated with a social security plan * Informed consent signed prior to any specific study-related procedures Exclusion Criteria: * Men (no marketing authorization for CDK4/6 inhibitors in men in France) * Previous systemic treatment for metastatic disease (chemotherapy, hormone therapy, etc.) * Previous treatment with a CDK4/6 inhibitor (adjuvant or for m…