3:09 PM Abstract No. 265 Comparative evaluation of outcomes following microwave ablation of central versus peripheral renal tumors

Abstract

Radiofrequency and cryoablation of renal tumors demonstrate increased rates of local tumor recurrence in central compared to peripheral tumors. However, there is limited data on the effectiveness of microwave ablation in a similar setting. This study assessed the efficacy of microwave ablation in the setting of central versus peripheral tumors. An IRB-approved single-center retrospective study was performed to identify patients that underwent percutaneous microwave ablation of renal tumors over a three-year period (2015-2018). These patients were divided into two cohorts based on central versus peripheral tumor location. Central renal tumors were defined as being within 4 mm of a major calyx, renal pelvis, and/or ureter. Primary response rates were defined as complete tumor response after a single microwave ablation. Secondary response rates were defined as complete response following repeat microwave ablation of local tumor recurrence. Statistical analysis was performed with GraphPad Prism 8 (La Jolla, CA). A total of 153 microwave ablations were performed on 48 central and 93 peripheral renal tumors. There was a significantly higher primary response rate for peripheral compared to central tumors (0.91 vs. 0.79, P = 0.04). There was also a higher secondary response rate for peripheral compared to central tumors, although the result was not statistically significant (1.0 vs. 0.75, P = 0.20). There was no significant difference in average time to local recurrence between peripheral and central tumors (311.1 vs. 209.6 days, P = 0.41). The progression free survival at 1 and 2 years following microwave ablation was 94% and 83% for peripheral tumors and 89% and 67% for central tumors (P = 0.27). There was a significantly higher primary response rate for microwave ablation of peripheral compared to central renal tumors. There was no statistically significant difference in secondary response rate between peripheral and central tumors, which suggests that central tumors may be successfully treated with repeat microwave ablation. These findings are in concordance with previously reported results from radiofrequency and cryoablation.