Material and Method: Radiofrequency ablation was performed on 409 tumors in Siriraj Hospital between October 2009 and May 2012. Eighty-eight nodules in 78 patients were treated by RF ablation, which divided into high risk and non-highrisk location. Complete ablation rate, residual tumor, recurrent tumor, and complication were retrospectively reviewed.

Results: HCC nodules were in non-high-risk location 34 nodules (38.6%) and in high-risk location 54 nodules (61.4%). Complete tumor ablations were done in 34 nodules (100%) of non-high-risk location group and 50 nodules (92.6%) of high-risk location group. All residual tumors were four nodules (7.2%), which located in subcapsular location. Recurrent tumors were found in six nodules (6.8%), and mean time to recurrence were 210.2 days. Early complication was 10.2% and late complication was 4.5%. The recurrent tumor and complication were not significantly different between two groups.

Conclusion: Radiofrequency ablation is effective treatment of hepatocellular carcinoma in high-risk location tumor. There is no significant difference in complication and tumor recurrent rate between high-risk and non-high-risk group. However, incidence of residual tumor is significantly increased in subcapsular location tumor.

Keywords: Radiofrequency ablation (RFA), Hepatocellular carcinoma (HCC), Complication, High-risk location