Integrated Testing Strategy for Simultaneous Detection of ESR-1 and gBRCA Mutations Via Liquid Biopsy in HR+/HER2- Metastatic Breast Cancer (mBC) Patients,

Inclusion Criteria: * Participants must have a confirmed diagnosis of estrogen receptor-positive (ER+) and/or progesterone receptor-positive (PgR+) breast cancer through histological and/or cytological examination by the local laboratory Participants must exhibit HER2-negative breast cancer 1. or 2+). If IHC is 2+, a negative in situ hybridization (Fluorescent in situ hybridization (FISH), Chromogenic in situ hybridization (CISH), or Silver-enhanced in situ hybridization (SISH)) test is required by local laboratory testing. * Participants should be in an advanced or metastatic setting including both those prior to the initiation of treatment for metastatic disease and those who experienced progression following treatment with cyclin-dependent kinases (CDK)4/6 inhibitors. However, the primary tumor should be treated according to the standard of care. * Written informed consent must be signed and dated by the patient and the investigator prior to inclusion. Exclusion Criteria: * Unable to provide written informed consent