Inclusion Criteria:  Women ≥18 years old Histologically confirmed hormone receptor-positive HER2-negative invasive breast cancer Hormone receptor-positive defined as 1% to 100% of tumor nuclei positive for Estrogen - - Receptor and/or Progesterone Receptor, as per ASCO/CAP Guideline 2020 - or Allred score of ≥3 HER2-negative defined as IHC result is 0/1+ or 2+ with ISH negative as per ASCO/CAP Guideline 2018 Diagnosed with de novo or recurrent metastatic breast cancer between January 2018 -and December 2020 Public health system or private health system  Exclusion Criteria:  Male Breast Cancer First-line treatment for mBC received through clinical trial