A Real-world Study Observing Treatment Patterns and Clinical Results for Patients in China With Hormone Receptor-positive, HER2-negative Metastatic Breast Cancer.

The study consists of both retrospective and prospective components, defined relative to the index date.

Inclusion Criteria \* Must be competent and able to comprehend, sign, and date an Institutional Review Board or Institutional Ethics Committee approved Informed consent form (ICF) before participating in the study. OR Eligible for exemption from informed consent (for patients who die or became lost to follow-up within 2 months of initiating 2L therapy). \* Chinese men or women ≥ 18 years old at time of consent. \* Pathologically documented breast cancer that: a) is unresectable or metastatic. b) is HR+/HER2- (IHC 2+/ISH- or IHC 1+ or IHC 0, with/without membrane staining) based on the most recent test result \* Planning to initiate 2L treatment or initiated 2L systemic therapy within 2 months prior enrollment as per the prescription or medical records. Exclusion Criteria \* Patients who plan to participate in any blinded interventional clinical trial in 2L setting.