Bilateral atypical femur fracture in a patient with breast cancer taking zoledronic acid and denosumab: A case report.

A 54-year-old woman developed stage IV breast cancer 8 years prior. Chemotherapy was administered, and she was started on zoledronic acid treatment for her bone metastases. Her chemotherapy regimen was then switched, owing to disease progression. Fifty-seven months after starting treatment with zoledronic acid, the patient suffered an atypical femoral fracture of her right femur, for which she underwent surgery. Twenty months later, she developed another atypical femoral fracture in her left femur and underwent intramedullary nail fixation. Zoledronic acid and denosumab use in patients with metastatic bone tumours caused by breast cancer should be done cautiously, considering atypical femoral fracture risk.