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

The purpose of this real-world study is to look at breast cancer patients receiving Palbociclib using a large real-world database collected under real-world practice. This study also looks at the safety of Ibrance, including any side effects. Side effects are undesired effects of a medicine or other type of treatment. This study will include the data of the following participants: * Adult women (more than18 years of age) with at least one visit with a breast cancer * Patients with locally advanced breast cancer or metastatic breast cancer with a staging classification of stage III, stage IV. Advanced cancer is a term that is often used to describe cancer that is unlikely to be cured. Metastatic cancer is the cancer which is spread from the place where it started to other places in the body. * Patients with a laboratory test positive for hormone receptor and negative for HER2 before or up to 60 days after advanced/metastatic breast cancer diagnosis date. * Patients who received at least one initial prescription of Ibrance following a diagnosis of advanced/metastatic breast cancer. This study will look at the safety of palbociclib treatment by looking at the number and severity of the side effects.