Study of S-1 Oxaliplatin (SOX) for Biliary Tract Cancer (BTC) (Ampullary Adenocarcinoma)

Inclusion Criteria: 1. Informed consent has been signed by the subject itself; 2. Aged over 18; 3. With a definite pathological or cytological diagnosis of adenocarcinoma; 4. No pre-treatment (including radiotherapy, chemotherapy, immunotherapy, etc.). For recurrent cases, if the subjects have received adjuvant chemotherapy without S-1 or L-OHP after surgery and the time to the end date of adjuvant chemotherapy is over 6 months, they can also be enrolled; 5. Enhanced helical CT or MRI scanning shows a target lesion over 1cm within 14 days before enrollment 6. Within 7 days before enrollment, baseline blood routine and biochemical indicators meet the following criteria: * Hemoglobin ≥ 90g/L, * Absolute neutrophil count (ANC) ≥ 1.5 × 109/L, * Platelets ≥ 100×109/L， * Serum total bilirubin \< 1.5 times of the upper normal limit, * Serum creatinine \< upper limit of normal, * Serum albumin ≥ 30 g/L; 7. Can receive oral administration; 8. Karnofsky(KPS) score ≥ 70 points; 9. Expected survival time is more than 90 days; 10. Women of childbearing age must receive urine or blood pregnancy test within 7 days before randomization and the results are negative; 11. Male and female patients of appropriate reproductive age are willing to use reliable contraception methods for contraception in the process of study till 30 days after drug withdrawal. Exclusion Criteria: 1. Patients with a severe drug allergy history (including mildly allergic to L-OHP, 5-FU, FT207, 5-HT3 receptor antagonist); 2. Patients who participated or are participating in other clinical trials within 4 weeks before enrollment; 3. Patients who have received blood transfusion, blood products and hematopoietic factor preparations such as G-CSF within 15 days before enrollment; 4. Patients who have undergone a surgery within 15 days before enrollment, and its effects have not been eliminated; 5. Patients with diarrhea; 6. Patients with a complication of active infection (infection causes a fever above 38 ℃); 7. Patients accompanied by dysphagia, complete or incomplete gastrointestinal obstruction, active gastrointestinal bleeding and perforation, etc. that cause difficulty in taking S-1 orally; 8. Patients with severe liver disease (e.g. active hepatitis, cirrhosis, etc.), renal insufficiency, severe lung disease (interstitial pneumonia, pulmonary fibrosis, severe emphysema, etc.), or uncontrollable diabetes, hypertension and other chronic systemic diseases; 9. Patients who have received long-term systemic steroid therapy (Note: short-term users with steroid withdrawal \> 2 weeks can be selected); 10. Patients with brain metastases or suspected of brain metastases; 11. Patients with peripheral nervous system disorder or a history of significant mental disorder and central nervous system disorder; 12. Heart disease of significant clinical symptoms, e.g. congestive heart failure, coronary heart disease with significant symptoms, arrhythmia and hypertension that are difficult to be controlled by drugs, or with an episode of myocardial infarction within 6 months, or cardiac insufficiency; 13. Patients with pleural effusion, ascites, or pericardial effusion that needs drainage; 14. Pregnant or breast-feeding women, or male and female patients of appropriate reproductive age who refuse to take contraceptive measures; 15. Patients who have suffered from other malignancies within 5 years, except basal cell carcinoma and carcinoma in situ of uterine cervix that have already been cured; 16. Patients without legal capability, or who can not continue the study due to medical or ethical reasons; 17. Patients who are determined not suitable to participate in this clinical trial by the investigators.