US-guided percutaneous microwave ablation of renal cell carcinoma: intermediate-term results

To retrospectively review intermediate-term (median, 20.1 months) clinical outcomes after microwave ablation (MWA) of renal cell carcinoma (RCC).

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.

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.

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.