NGS as the First-line Treatment in Advanced Biliary Tract Cancer

Inclusion Criteria: 1. histologically confirmed locally advanced or metastatic biliary tract carcinoma (including intrahepatic bile duct, extrahepatic bile duct, gallbladder and ampulla of vater); 2. no history of chemotherapy or radiotherapy for biliary tract cancer, except those delivered as adjuvant setting that completed at least 6 months before documentation of recurrence by imaging study. 3. presence of at least one measurable tumor lesion which is defined as lesions that can be accurately measured in at least 1 dimension with longest diameter (LD) ≥20 mm using conventional techniques or ≥10 mm with spiral CT and MRI; measurable lymph nodes must be ≥15 mm in the short axis; 4. adequate hematopoietic function which is defined as below: 1. hemoglobin level ≥ 9 g/dL; 2. absolute neutrophil count (ANC) ≥ 1,500/mm3; 3. platelet count ≥ 100,000/mm3; 5. adequate hepatic function which is defined as below: 1. total bilirubin \< 2 mg/dL; 2. Alanine aminotransferase (ALT) ≤ 3 x ULN; ≤ 5 x ULN if liver metastasis 6. adequate renal function: creatinine clearance rate (CCr) ≥ 50 mL/min ((based upon Cockroft-Gault formula or 24-hour urine collection); \< Cockroft-Gault formula \> Male: ((140 - age) × weight \[kg\])/(72 × serum creatinine\[mg/dL\]) Female: 0.85 x estimate for male 7. age of 20 years or above; 8. ECOG performance status 0-1; 9. life expectancy of at least 12 weeks; 10. patients with childbearing potential shall have effective contraception for both the patient and his or her partner during the study. 11. ability to understand and willingness to sign a written informed consent document. Exclusion Criteria: 1. other malignancy within the past 5 years except for adequately treated basal or squamous cell skin cancer or cervical cancer in situ; 2. history or known presence of brain metastasis; 3. presence of grade 2 or above ascites or pleural effusion; 4. presence of grade 2 or above diarrhea; 5. presence of mental disease or psychotic manifestation; 6. active or uncontrolled infection; 7. significant medical conditions that is contraindicated to study medication or render patient at high risk from treatment complications based on investigator's discretion; 8. pregnant women or nursing mothers, or positive pregnancy test for women of childbearing potential. 9. History of active autoimmune disease within 3 years or long-term use of steroid more than prednisolone 10mg/day.