Advanced biliary tract adenocarcinoma has a poor prognosis with limited therapeutic options. Nab-paclitaxel plus S-1 chemotherapy will be given to untreated patients with advanced biliary tract adenocarcinoma for the first-line treatment.

Gemcitabine/Nab-paclitaxel has become a standard therapy in advanced pancreatic cancer. Given the morphologic and histologic similarities between pancreatic cancer and biliary tract adenocarcinoma, nab-Paclitaxel may be a promising regimen, and S-1 has been approved for biliary tract cancer in Japan. Untreated patients with advanced biliary tract adenocarcinoma will receive Nab-paclitaxel 120 mg/m2 (D1, D8, q3w) and S-1 (40mg BID for body surface area<1.25 m2; 50mg BID for body surface area of 1.25-1.5 m2; and 60mg BID for body surface area>1.5 m2; D1-14, q3w) as the first-line treatment. The investigators will investigate the efficacy and safety of the combination treatment, and expect to provide a more effective treatment plan for patients with advanced biliary tract cancer in China.The primary endpoint is objective response rate(ORR), and the secondary endpoints are progression-free survival(PFS), overall survival(OS) and the safety.

Inclusion Criteria:

• Age, years: 18-70
• Histologically and cytologically confirmed advanced biliary tract adenocarcinoma, unresectable, measurable lesions according to RECIST criteria; ECOG score of 0-1; life expectancy ≥12 weeks;
• Untreated; more than 6 months after the last adjuvant chemotherapy (does not include taxanes and S1);
• Laboratory examination within 14 days before entering the study should meet following requirements:

ANC ≥ 1.5 x 10^9/L; PLT ≥ 100 x 10^9/L; Hb ≥ 90g/L (9g/dL); AST, ALT ≤ 2.5 x ULN (with no liver metastasis), ≤ 5 x ULN（with liver metastasis); creatinine ≤ 1.5 x ULN; TBIL ≤ 1.5 x ULN

• Both male and female subjects of potential fertility have to agree effective birth control during the entire study
• Informed consent

Exclusion Criteria:

• Concurrent other effective treatment (including radiotherapy)
• Resectable patients
• Allergy history to other drugs in the same class patients with pregnancy or lactation
• Known severe internal medical diseases
• Abnormal heart function or relevant history of myocardial infarction and severe arrhythmia
• Immunocompromised patients, such as HIV positive
• Uncontrollable mental illness
• Other conditions the researchers considered ineligible for the study