Outcomes For A Multi-Institutional Cohort Of Patients Treated With Intra-Operative Radiation Therapy For Advanced Or Recurrent Renal Cell Carcinoma

442 Background: For patients with advanced or locally recurrent (LR) renal cell carcinoma (RCC), the role of intra-operative radiation therapy (IORT) remains controversial. We analyzed outcomes in a multi-institutional cohort of patients with RCC who received IORT.Between 1985 and 2010, 98 patients were treated with IORT for advanced or LR RCC at 9 institutions. We collected demographic, clinical, treatment, and outcomes data for all patients. Overall (OS), disease specific (DSS), and disease-free survival (DFS) was estimated using the Kaplan-Meier method. A multivariate Cox hazards regression was used to test significance.IORT was delivered at nephrectomy for advanced disease (28%) or during resection of LR RCC in the renal fossa (72%). 69% of patients were male and mean age at RCC diagnosis was 57. At initial nephrectomy, primary T-stage was 17% T1, 12% T2, 55% T3, and 16% T4. Prior to IORT, 87% had visibly complete surgical resection of tumor. Mean IORT dose delivered was 14.7Gy (range 9-20Gy). Average post-op hospitalization was 10.7 days. Median follow-up after IORT was 1.6 years. OS at 1 and 5 years after IORT was 69% and 37% for advanced patients and 94% and 55% for LR patients, respectively. DFS at 1 and 5 years was 72% and 39% for advanced patients and 96% and 52% for LR patients, respectively. DSS at 1 and 5 years was 72% and 41% for advanced patients and 96% and 60% for LR patients, respectively. For the entire cohort, higher IORT dose (HR 1.3, p < 0.001), positive initial node status (HR 2.9-3.6, p < 0.01), and presence of sarcomatoid features (HR 3.7-6.9, p < 0.05) had a significant association with decreased OS, DFS and DSS. Patients who received adjuvant systemic therapy after IORT showed decreased DSS (HR 2.4, p = 0.03). When analyzing LR tumors alone, positive margin (HR 2.6, p = 0.01) was associated with decreased OS.We report on the largest known cohort of patients with RCC managed with IORT and we have identified factors associated with survival. Outcomes in our cohort with LR RCC treated with local resection and IORT compare favorably to similar groups treated with resection alone suggesting improved DSS may be possible with IORT.