MP54-06 RADIOFREQUENCY ABLATION OUTCOMES BASED ON RENAL CELL CARCINOMA HISTOLOGIC SUBTYPES

INTRODUCTION AND OBJECTIVES: Radiofrequency ablation (RFA) has been used as a successful modality for treating small renal masses in a minimally invasive, nephron sparing manner. Ablation failures are generally attributed to a vascular heat sink phenomenon. The vascularity, and thereby enhancement pattern, of RCC subtypes varies such that RFA success may be impacted. We sought to determine if outcomes for RFA ablation were significantly different based on RCC subtype. METHODS: All RFAs from two centers with extensive experience in performing RFA were reviewed. Only those with RCC subtype of clear cell or papillary RCC were included in the analysis. Other RCC subtypes (chromophobe n1⁄48, oncocytic neoplasm n1⁄49, mixed n1⁄42) were each small and not included. RFA failure was defined as a >10 HU enhancement on contrast-enhanced CT in a previous zone of ablation. Disease-free survival (DFS) was defined as those patients who had no evidence of disease, either as initial ablation failures or as late recurrences. Groups where compared using the chi-squared or exact T test. The Kaplan-Meir method, using the log-rank test, was used to compare outcomes between RCC histologic subtypes. RESULTS: A total of 229 patients were included in the analysis. The mean age of the cohort was 64.5 +/13.8 years with a median follow-up of 48 (IQR 12-65) months. The mean tumor size of the cohort was 2.5 +/0.8 cm. There was no difference between the papillary and clear cell RCC groups based on age, tumor size or months of follow-up. A total of 181 (75.7%) tumors were clear cell type and 48 (20.1%) papillary type. There were 15 failures in the clear cell subtype and 0 in the papillary subtype, giving an estimated 5-year DFS of 89.7% and 100% for clear cell RCC and papillary RCC respectively (p1⁄40.041). CONCLUSIONS: This is the first report suggesting a significant difference in RFA success based in RCC subtype, with papillary RCC having more favorable outcomes compared to clear cell RCC. Based on this data, further studies looking at how best to follow RFA treated tumors based on subtype is warranted.