Complete Radiographic Response to Zoledronic Acid Therapy in a Patient With Bony Metastatic Urothelial Carcinoma: A Case Report.

Zoledronic acid (ZA) is commonly used for the prevention of skeletal-related events (SREs) in patients with bony metastases. ZA is a bisphosphonate that inhibits osteoclasts, possibly through inhibition of proto-oncogenic Ras activity in osteoclasts by interfering with normal post-translational modifications of Ras. This would suggest that ZA could induce an objective tumor response in metastatic tumors in bone that harbor oncogenic Ras, as the oncogenic Ras in these tumors would require similar post-translational modifications. We recently cared for a patient with biopsy confirmed metastatic urothelial carcinoma who demonstrated a complete radiographic response to ZA. His tumor harbored an oncogenic K-Ras protein, supporting the possibility of interference with Ras activity as the mechanism for the radiographic complete response.