ctDNA Detection of MRD in Predicting Postoperative Recurrence in Biliary Tract Cancers：A Multicenter Prospective Trial

Inclusion Criteria: 1. Male or female ≥ 18 years of age on the day of signing informed consent. 2. Clinically diagnosed as BTC before surgery and confirmed by pathology after surgery. 3. Stage I-III tumor according to the UICC/AJCC TNM staging system (8th edition in 2017), meeting the indications for radical surgery and are planned to undergo radical treatment. Those who do not undergo radical surgery will be excluded. 4. Patients must have a performance status of ≤1 on the ECOG Performance Scale. 5. Patients must have survival of \> 6 months after surgery 6. Serological tumor indicators (CEA, CA19-9) and imaging data ( CT and/or MRI, PET-CT) were complete. 7. Blood biochemical indicators meet surgical standards 8. Written informed consent must be obtained from patient or patient's legal representative and ability for patient to comply with the requirements of the study. Exclusion Criteria: 1. Patients with recurrent biliary tract tumors 2. Patients with hepatobiliary mixed tumors 3. Patients with malignant tumors of other organs that have not been cured before. 4. History of organ transplant or allogeneic stem cell transplant 5. Patients with severe infections that are active or poorly controlled clinically 6. patients who are cognitively impaired or with known psychiatric disorders, and/or substance abuse 7. pregnant or lactating women 8. Failed to sign informed consent 9. Other conditions that researchers judged inappropriate for inclusion