Increase of vertebral fractures in patients with metastatic breast cancer treated with endocrine therapy combined with CDK 4/6 inhibitor

CDK4/6 inhibitors (CDK4/6i) combined with endocrine therapy (ET) represent the standard of care for HR-positive, HER2-negative metastatic breast cancer (mBC). ET increases the risk of bone fracture; moreover, it has been suggested that CDK6 plays a critical role in controlling osteoblast, osteoclast, and chondrocyte differentiation. The possible impact of ET combined with CDK4/6i on bone health has not already been explored. The main aim of the current study is to evaluate the proportion and the evolution of vertebral fractures (VFs) in mBC HR+ patients (pts) treated with ET combined with CDK4/6i.