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, andgallbladder carcinoma);
3. Confirmed as adenocarcinoma by histology;
4. Has not received systemic therapy in the past (patients who have not progressed withinsix months after the completion of neoadjuvant therapy or adjuvant therapy can beenrolled);
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-linetreatment;
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; Unableto collect baseline plasma or tissue samples.