Inclusion Criteria:  Age ≥18 years old. HR+/HER2- BC diagnosis with confirmed metastatic/locally advanced disease. Patient initiated on palbociclib (regardless the line of therapy) within the period between 01st January 2015 and 01st March 2019. Minimum of six months of follow up data since palbociclib initiation. Received palbociclib plus aromatase inhibitor or palbociclib plus fulvestrant in line with the licensed indication(s).  Exclusion Criteria:  Prior or current enrolment in an interventional clinical trial for metastatic/locally advanced BC. Patients who were initiated on palbociclib after 01st March 2019.