Pembrolizumab in Biliary Tract Cancer

Inclusion Criteria: * A histopathological / cytological diagnosis of non-resectable or recurrent / metastatic biliary tract carcinoma (intra- or extra-hepatic) or gallbladder * Availability of archival FFPE tumor tissue for biobanking * Measurable disease by CT/MRI (RECIST 1.1) within 28 days of enrollment * ECOG performance status 0, 1 * Age ≥ 18 with estimated life expectancy \>3 months * Adequate hematological function: screening labs should be performed within 14 days (± 3 days) prior to enrollment: * Hemoglobin ≥ 10 g/dl\* (prior transfusions for patients with low hemoglobin are allowed) * White blood cell (WBC) ≥ 3.0 x 109/L * Absolute neutrophil count (ANC) ≥ 1.5 x 109/L * Platelet count ≥ 100 x 109/L * Adequate liver function: screening labs should be performed within 14 days (± 3 days) prior to enrollment: * Total bilirubin ≤ 1.5 x upper limit of normal (ULN) * ALT and/or AST \& alkaline phosphatase ≤ 5 x ULN * Adequate renal function: screening labs should be performed within 14 days (± 3 days) prior to enrollment: * Serum creatinine \< 1.5 x ULN * and a calculated GFR ≥ 45 mL/min (using Cockcroft-Gault formula). If the calculated GFR is below 45 mL/min, isotope EDTA confirmation of adequate renal function is required (see Appendix F). If isotope EDTA methods are not available, then a 24-hour urine creatinine clearance can be used. * Adequate coagulation: screening labs should be performed within 14 days (± 3 days) prior to enrollment: * International Normalized Ra…