The effect of zoledronic acid on bone metastasis in patients suffering from renal cell cancer (RCC): A German prospective single-arm clinical trial

5107 Background: The incidence of RCC increased over the last decades and about 30% of patients will develop bone metastasis. These pts. face considerable skeletal morbidity e.g. bone pain, pathologic fractures, spinal cord compression or tumor induced hypercalcemia (TIH). A prospective trial was initiated in RCC metastatic to bone evaluating the SRE (skeletal related event) rate under therapy with zoledronic acid (ZA). Primary objective was the proportion of pts. with at least one SRE after 12 months. Methods: Patients with RCC must have had ≥1 bone metastasis and ≤2 prior applications of a bisphosphonate. Bone lesions were diagnosed by bone scan and ≥1 lesion was confirmed using X-ray, CT or MRI. Pts. passed a 12 months treatment period receiving 4 mg ZA every 3 weeks. Pts. were followed every 3 weeks for 54 weeks for development of SREs (radiation or surgery to bone, spinal cord compression, pathologic bone fractures) and TIH. A bone scan was done, if AP or LDH were >2xULN or symptoms occurred. Suspect...