Minimally interventional study on prevalence of emerging ESR1 mutations in liquid biopsy in three cohorts of patients with breast cancer (with and without prior therapies in metastatic setting, and during first-line aromatase inhibitor plus CDK4/6 inhibitor therapy) in comparison with patient's baseline ESR1 mutation status as defined by tissue profiling.
BC patients, male and female,
18 years old and older,
Pre or post menopausal,
With HR+ (ER and/or PR positive) and Her-2 negative (confirmed centrally),
Patients WITHOUT HR+ (ER- and/or PR-positive)/HER2-negative disease,
Patients without radiological and/or pathological confirmation of locally unresectable and/or metastatic breast cancer,
Patients who are NOT candidates for further systemic treatment following a diagnosis of metastatic disease or disease progression,
Patients who have already started a CDK4/6 inhibitor in combination with endocrine therapy (with or without ovarian suppression) for first-line metastatic disease (for Cohort 1);