The purpose of this study is to evaluate the clinical feasibility and short-term outcome of switching monopolar RFA using a separable cluster electrode in patients with primary and secondary liver malignancies.

Radiofrequency ablation (RFA) is one of minimal invasive treatment methods and it has been showing comparable overall survival with surgery in early or small hepatocellular carcinomas (HCCs) and better cost-effectiveness. However, it is suffering from high local tumor progression (LTP) rate. To reduce LTP rate, creation of large ablative zone has been attempted in various strategies. A separable cluster electrode is a new type of RFA electrode. It consists of three individual applicators and the applicators can be incorporated as a single handle such as a cluster electrode, and can be separated as three electrodes, depending on operators' needs. It allows high flexibility to operators and the preclinical results were promising. Herein, we want to evaluate the clinical feasibility of the electrodes by observing major complication rates, technical success rate and 12-months LTP rate.

Inclusion Criteria:

• Hepatic malignancies diagnosed on biopsy OR
• Typical imaging features of hepatocellular carcinoma (HCC) on computed tomography (CT) or magnetic resonance imaging (MRI) according to AASLD guideline
• Typical imaging feature of metastasis on CT or MRI AND
• 1~5 tumors equal to or smaller than 5cm in the liver
• no direct contact with or invasion into the hepatic hilar structures or inferior vena cava (IVC)
• Eastern Cooperative Oncology Group performance status of 0
• Patients who signed informed consent

Exclusion Criteria: Patients with any of followings are excluded.

• Patients with uncontrolled coagulopathy
• Patients with Child-Pugh classification C
• Patients with tumor invasion in major portal vein or hepatic vein branch
• Extrahepatic metastasis