A Study to Understand the Patients Confirmed to Have Advanced or Metastatic Breast Cancer and Receiving Palbociclib Treatment Using a Real-world Database

Inclusion Criteria Patients must meet all of the following inclusion criteria to be eligible for inclusion in the study: * Adult women (≥ 18 years of age) with at least one visit with a breast cancer ICD10 diagnosis code (C50.x) * Patients with locally advanced breast cancer or metastatic breast cancer with a staging classification of stage III, stage IV (distant metastases). * Patients with a laboratory test positive for hormone receptor (HR) and negative for human epithelial growth factor receptor 2 (HER2) before or up to 60 days after advanced/metastatic breast cancer diagnosis date. 1. HR-positive is defined as any positive test for estrogen receptor or progesterone receptor. 2. HER2-negative is defined as any HER2-negative test and the absence of a positive test (immunohistochemistry positive (3+), fluorescence in situ hybridization positive/amplified). * Patients who received at least one initial prescription of Ibrance following a diagnosis of advanced/metastatic breast cancer Exclusion Criteria Patients meeting any of the following criteria will not be included in the study: * Breast cancer with HR-negative and HER2-positive on laboratory testing. * More than a 90-day gap between breast cancer diagnosis date and next visit. * Patients who treated as off-label