Hypofractionated Radiation Therapy and Bintrafusp Alfa for the Treatment of Advanced Intrahepatic Cholangiocarcinoma

Inclusion Criteria: * Patients must be male or female \>= 18 years of age * Patients with histologically or cytologically confirmed intrahepatic cholangiocarcinoma. There must be at least two measurable tumors. One larger mass that will be radiated and a secondary metastatic site that is amenable to biopsies * Patients must have received at least one standard first-line chemotherapy regimen or have refused chemotherapy * Patients with measurable disease assessed at baseline by computed tomography (CT) (or magnetic resonance imaging \[MRI\] where CT is contraindicated) will be entered in this study * Eastern Cooperative Oncology Group (ECOG) performance status 0-1 (Karnofsky \> 70) * Leukocytes \>= 3,000 cells/mm\^3 * Absolute neutrophil count \>= 1,500 cells/mm\^3 * Platelets \>= 100,000 cells/mm\^3 * Hemoglobin \>= 9 g/dl (no blood transfusions within 4 weeks prior to enrollment) * Total bilirubin \< 1.5 x institutional upper limit of normal (IULN) * Aspartate aminotransferase (AST) (serum glutamic-oxaloacetic transaminase \[SGOT\])/alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase \[SGPT\]) =\< 2.5 x IULN without liver metastasis, =\< 5 x IULN for patients with liver metastasis * Creatinine within normal institutional limits OR creatinine clearance \>= 60 mL/min/1.73 m\^2 for patients with creatinine levels above institutional normal * Women of childbearing potential (defined as not post-menopausal for 65 days or no previous surgical sterilization) and …