Endoscopic Radiofrequency Ablation for Unresectable Cholangiocarcinoma

The goal of this clinical trial is to learn about radiofrequency ablation in patients with unresectable bile duct cancer who receive systemic chemotherapy and bile duct stenting. The main questions it aims to answer are: * Does radiofrequency ablation of tumorous bile duct occlusion reduce risk of complications in these patients (eg stent dysfunction, delay of chemotherapy, infections etc)? * Is radiofrequency ablation safe in these patients? All participants will receive standard treatment with systemic chemotherapy and bile duct stenting. Researchers will compare two groups (one group will receive additional radiofrequency ablation, the other not).