1211 Stereotactic Radiosurgery is Highly Effective for the Treatment of Renal Cell Carcinoma Spinal Metastases

INTRODUCTION: Renal cell carcinoma (RCC) spinal metastases are traditionally radioresistant to conventional external beam radiotherapy (EBRT), leading to progression in pain and neurological deficit in patients who are refractory to treatment. Stereotactic radiosurgery (SRS) can deliver higher doses of radiation in fewer fractions which may overcome radioresistance. METHODS: From 2003-2023, 85 patients (122 lesions) undergoing SRS for RCC spinal metastases were analyzed. Patient demographics and clinical characteristics were recorded, including treatment history, neurologic status, pain quality, dosimetry and fractionation schedule, local control (LC), and overall survival (OS). RESULTS: Eighty-five patients (31% female) with 122 lesions in the cervical (11%), thoracic (50%), lumbar (27%), and sacral (12%) spine were treated with SRS. The median patient age was 61 years (range:39-91). The median follow-up period was 8 months (range:1-125). Treatment was delivered in a median of 1 session (range:1-3) with a prescription dose of 20Gy (range:14-30) to a gross tumor volume of 37.4cc (range:0.8-208.2). Pain was reported to have improved or remained stable for 89% of lesions. Twenty-four lesions (20%) locally progressed. The 6-, 12-, and 18-month LC rates were 91%, 83%, and 76%, respectively. The median OS was 12.3 months. On multivariate analysis, prior EBRT was associated with worsened OS (HR:1.89, 95th CI:[1.05-3.40], p=0.035) and multi-session SRS was associated with improved OS (HR:0.45, 95th CI:[0.23-0.90], p=0.023). There were 8 (7%) instances of radiation-induced adverse effects [5 (4%) acute pain flares, 2 (1.6%) vertebral compression fractures, and 1 (0.8%) radiation proctitis]. CONCLUSIONS: The efficacy of conventional EBRT for RCC spinal metastases has been limited given the radioresistance of RCC. Spinal SRS is an effective alternative treatment modality that offers high rates of local tumor control and symptom relief for patients with RCC spinal metastases.