US-guided Percutaneous Microwave Ablation of Renal Cell Carcinoma: Intermediate-term Results

Purpose: To retrospectively review intermediate-term (median, 20.1 months) clinical outcomes after microwave ablation (MWA) of renal cell carcinoma (RCC). Materials and Methods: This retrospective study was approved by the institutional review board. The results from 46 patients with 49 RCC nodules (diameter, 0.6-7.7 cm; mean, 3.0 cm +/- 1.5 [standard deviation]) treated with ultrasonography (US)-guided percutaneous MWA with cooled-shaft needle antenna from April 2006 to December 2010 were reviewed. One antenna was used for tumors smaller than 2 cm; two, for tumors 2 cm or larger. The patients were followed up with contrast material-enhanced US and computed tomography or magnetic resonance imaging at 1, 3, and 6 months and every 6 months thereafter. The effect of changes in key parameters (including overall survival, disease-free survival, and local tumor progression rate) was statistically analyzed by using the log-rank test. Results: Technical effectiveness (complete ablation at follow-up enhanced imaging 1 month after MWA) was achieved in 48 of 49 (98.0%) tumors, and the metastasis-free rate was 100% (46 of 46). The 1-, 2-, and 3-year local tumor progression rates were 4.6%, 7.7%, and 7.7%, respectively. The cancer-specific survival rate was 100% (46 of 46), and 1-, 2-, and 3-year overall survival rates were 100%, 100%, and 97.8%, respectively. The 1-, 2-, and 3-year disease-free survival rates were 95.4%, 92.3%, and 92.3%, respectively. No major complications occurred. Multivariate analysis showed that tumor number (P = .046), tumor growth patterns (P = .003), and ablation time (P = .04) were independent unfavorable prognostic factors. Conclusion: In the intermediate term, US-guided percutaneous MWA appears to be a safe and effective technique for the management of RCC, especially small RCC, in selected patients. (c) RSNA, 2012