Safety of Biliary Intraductal Radiofrequency Ablation in Patients With Unresectable Extrahepatic Biliary Tract Cancer

Inclusion criteria 1. Male or female ≥18 years old. 2. Histologically or cytologically confirmed diagnosis of previously untreated and unresectable\*, locally advanced and/or metastatic extrahepatic biliary tract cholangiocarcinoma with obstructive jaundice (increased serum level of total bilirubin). 3. ECOG performance status 0 to 2. 4. Adequate bone marrow function: Neutrophil count ≥1.0 x 109/L, platelet count ≥100 x 109/L. 5. Adequate renal function in case of cisplatin administration: Estimated Glomerular Filtration Rate (eGFR) ≥60mL/min/1.73m2. 6. Willing and able to provide written informed consent. 7. Planned initiation of any standard-of-care systemic anti-proliferative therapy against ETB. \*The reason for inoperability needs to be documented and categorized as follows: * Wish of patient. * Locally advanced or vascular invasion = surgically not removable. * Remnant liver is not sufficient. * Anatomic contraindications. * Distant metastasis. * Severe comorbidities. * Other reasons. Exclusion criteria <!-- --> 1. Solely intrahepatic cholangiocarcinoma or mixed type liver tumors (cholangiocarcinoma with hepatocellular differentiation parts). 2. Multiple hepatic metastases with significant blockage of one or more liver segments and/or less than 50% of liver parenchyma potentially drainable on pre-intervention imaging. 3. In case of immune-checkpoint-inhibitor (ICI) administration, any autoimmune diseases including inflammatory disorders such as Crohn's disease, ulcerative colitis, Wegener granulomatosis, systemic lupus erythematosus, rheumatoid arthritis, Graves' disease. Exceptions: \- Hypothyroidism following Hashimoto thyroiditis stable on hormone replacement. \- Patients with vitiligo. \- Any chronic skin disorders that do not require systemic treatment. 4. Use of immunosuppressive medication within 3 weeks prior to ICI administration. Exceptions: \- Topical or inhaled steroids. * Systemic corticosteroids at physiologic doses not exceeding \>10mg/d of prednisone or equivalent. 5. Prior Self-Expandable Metal Stent (SEMS) placement in the biliary tree. 6. Biliary obstruction of non-tumoral etiology. 7. Platelets \<100 x 109/L or International Normalized Ratio (INR) \>1.5. 8. Secondary tumor. Exceptions: \- Tumor treated with curative intent without recurrence for more than 5 years. * Non-melanoma skin cancer treated carcinoma in situ without evidence of disease. 9. Pregnancy or lactation. 10. Known or suspected non-compliance, drug, or alcohol abuse. 11. Inability to follow the procedures of the study, e.g., due to language problems, psychological disorders, dementia, etc. of the candidate. 12. Participation in another interventional study within 30 days prior to enrollment. 13. Previous participation in the current study. 14. Other diseases like Human Immunodeficiency Virus, Liver cirrhosis Child-Pugh B or C, cardiac pacemaker, history of organ transplantation or condition likely to significantly decrease life expectancy i.e., life expectancy is less than 3 months according to investigator judgement.