Programmed Death Ligand (PD-L1) Combined With Chemotherapy for Patients With BTC

Inclusion Criteria: * Eighteen years and older; * Histological or cytological diagnosis of unresectable or metastatic gallbladder cancer or cholangiocarcinoma; * Previously untreated with systemic therapy; Subjects who developed recurrent disease \>6 months after a sort of adjuvant, neoadjuvant chemotherapy could also be eligible. * Liver function Child-Pugh A or B; * Performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG) Performance Status; * Life expectancy of at least 12 weeks; * At least one measurable lesion per RECIST 1.1; * Adequate organ function Exclusion Criteria: * Specific anti-tumor treatment prior to 4 weeks; * more than 50% liver metastasis ; * Patient with other serious diseases or clinical conditions, including but not limited to uncontrolled active infection etc; * History of severe hypersensitivity reaction to any monoclonal antibody or chemistry; * Women who are pregnant or in the period of lactation; * Patients with an active, known or suspected autoimmune disease. Patients are permitted to enrol if they have vitiligo, type I diabetes mellitus, residual hypothyroidism due to autoimmune condition only requiring hormone replacement;