A Study to Understand the Use of Palbociclib in Canadian Patients With Breast Cancer That Has Spread to Other Organs

The purpose of this real-world study is to understand the use of palbociclib as first treatment for Hormone receptor positive (HR+) and Human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer in Canada (PALCAN). The real-world study is not a research study. It involves real patients who receive medicines prescribed by their doctors in the real world. Metastatic breast cancer is the type which has spread from breast to other organs. HR positive stands for Hormone-receptor cells that have a protein on their surface that binds to one of 2 types of hormones. They are estrogen or progesterone. Both these hormones help cancer cells grow. HER2 negative describes cells that have a small amount or none of a protein called HER2 on their surface. In normal cells, HER2 helps control cell growth. Cancer cells that are HER2 negative may grow more slowly and are less likely to come back or spread to other parts of the body. This study will mainly measure: \- duration of treatment (from start of treatment till end of treatment) among a group of patients taking palbociclib (Ibrance) in combination with hormone therapy as first line treatment for HR+ HER2- metastatic breast cancer.