Breast cancer is the most common cancer in women worldwide, with more than two million new cases diagnosed in 2018. Overall survival rates for breast cancer vary globally, but in general they have improved, and in the UK, they have doubled over the past 40 years. In England, around 85% of women diagnosed with breast cancer survive for five years or more, and when diagnosed at its earliest stage, 98% of women survive for five years or more. However, this falls to 26% when breast cancer is diagnosed at its latest stage, known as stage IV or metastatic breast cancer. The low survival rate for metastatic breast cancer is in part because management of the condition remains challenging. However, there have been some positive developments for patients with metastatic breast cancer in the form of a new class of anticancer drugs known as cyclin-dependent kinase 4 and 6 (CDK 4/6) inhibitors. This article describes a service audit at an NHS trust in England investigating current practice regarding the use of CDK 4/6 inhibitors.