Observational Study on the Treatment of Patients With Metastatic Breast Cancer

This project aims to understand treatment patterns and outcomes in individuals with hormone receptor-positive \[HR-positive will be defined as Estrogen Receptor (ER) ≥ 1%\] and HER2-negative (HER2-Negative will be defined as IHC 0, 1+ and 2+/ISH-) unresectable or metastatic breast cancer (mBC) in Brazil. Ten Brazilian centers will participate. This study will consist of a convenience cohort; will be included 200 patients. Adult patients who had received treatment in the participant Brazilian centers, with mBC ER-positive (i.e. ER ≥ 1%) and HER2-negative (i.e. HER2 IHC 0, 1 or 2+ with negative ISH), and who had received any CDK4/6i as first-line treatment with any outcome (death, progressive disease, or drug interruption due to any cause) since January 2018 will be enrolled. Data will be extracted from digital charts of Brazilian participating institutions. Patients who were treated with a CDK4/6i since January 2018 will be enrolled.