Radiofrequency Ablation Combined With S-1 for Pancreatic Cancer With Liver Metastasis

Primary Outcome Measures: To evaluate the overall survival (OS) in pancreatic cancer patients with liver metastasis treated with radiofrequency ablation combined with S-1. Secondary Outcome Measures: 1. To explore the correlation of OS and serum microRNA of the patients. 2. To evaluate the progression free survival (PFS) and its correlation with serum microRNA. 3. To observe the objective response rate (ORR) and adverse effects of the treatment.