OBJECTIVE: To retrospectively evaluate the safety and short-term therapeutic efficacy of radiofrequency ablation (RFA) with a multiple-electrode switching system (MESS) to treat medium-sized (3.1-5.0 cm) hepatocellular carcinomas (HCCs). SUMMARY OF BACKGROUND DATA: Conventional monopolar RFA is limited in achieving local control for tumors larger than 3 cm. Therefore, MESS-RFA was developed, and can create a sufficiently large ablation volume including the target tumor and a 5−10 mm safety margin in medium-sized tumors METHODS: We performed a total of 168 RFAs with a MESS on 166 patients. The patients were treated under ultrasonographic guidance by percutaneous switching system RFA with a multichannel RF generator and two or three internally cooled electrodes. Technical effectiveness, local progression, and remote recurrence of HCC were determined. RESULTS: For the 166 isolated HCC tumors, the complete ablation rate of MESS-RFA was 98.79% (164/166). Mean ablation time per procedure was 12.33±3.01 min; mean ablation diameter was 5.79±0.61 cm. The complication rate was 2.41%. During follow-up (averaging 16.54 months), local tumor progression occurred in 15/166 patients (9.03%) with technical effectiveness, while new HCCs were detected in 40/166 patients (24.09%). Multivariate analyses revealed that local tumor progression was only associated with serum AFP levels above 100 ng/ml as a risk factor. CONCLUSION: MESS-RFA for achieving sufficient ablation volume is safe and efficient. This method also showed relatively successful therapeutic effectiveness on short-term follow up in the treatment of medium-sized HCCs.

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