Prospective Observational Study to Predict the Response of Biliary Tract Tumors to Immunotherapy

Inclusion Criteria: 1. Over 18 years old; 2. Imaging evaluation indicates unresectable advanced or metastatic biliary tract tumors (including intrahepatic cholangiocarcinoma, extrahepatic cholangiocarcinoma, and gallbladder carcinoma); 3. Confirmed as adenocarcinoma by histology; 4. Has not received systemic therapy in the past (patients who have not progressed within six months after the completion of neoadjuvant therapy or adjuvant therapy can be enrolled); 5. At least one measurable lesion according to RECIST 1.1 standard; 6. Plan to receive PD-1/PD-L1 inhibitors combined with chemotherapy as first-line treatment; 7. Sign informed consent, has good compliance and can cooperate with follow-up. Exclusion Criteria: 1. Suffering from other active malignant tumors within 5 years or simultaneously; Unable to collect baseline plasma or tissue samples.