• Histologically or cytologically confirmed hepatocellular carcinoma or biliary tract cancer

• Locally advanced/unresectable or metastatic disease

• Age ≥ 18 years at time of study entry

• ECOG Performance Status ≤ 1

• One previously unirradiated lesion amenable to 8 Gy x 3 radiotherapy based on dosimetric organ tolerance AND another unirradiated measurable lesion (per irRECIST) outside of the radiation field

• Immunotherapy-naïve

• Progressed on, be intolerant of, or refused sorafenib \[for HCC\], second line treatment and beyond for cholangiocarcinoma or gemcitabine-based chemotherapy for biliary tract cancer

• The benefits of sorafenib have been discussed with the patient and the patient has refused treatment with sorafenib.

• Viral status (Hepatitis B and C) must be known. All HBV-positive patients must be on antiviral medication for viral suppression.

‣ Patients with concomitant HBV infection must have a confirmed diagnosis of HBV characterized by the presence of hepatitis B core antibodies, and be sufficiently suppressed with active antiviral treatment (per local institutional practice) prior to enrollment to ensure adequate viral suppression (HBV deoxyribonucleic acid \[DNA\] \<2000 IU/mL).

⁃ Patients with concomitant HCV infection must have confirmed diagnosis of HCV characterized by the presence of detectable HCV ribonucleic acid (RNA or anti-HCV antibody upon enrollment.

• Body weight ≥ 30 kg

• Child-Pugh Score of A. A score of B7 is allowed without severe ascites or without hepatic encephalopathy.

• Adequate organ and marrow function, defined as:

‣ Hemoglobin ≥ 9 g/dL

⁃ ANC ≥ 1.5 x 10\^9/L

⁃ Platelet count ≥75×109/L

⁃ Serum bilirubin ≤2.0× the upper limit of normal (ULN).

⁃ ALT and AST ≤ 3 x institutional ULN

⁃ Albumin \> 2.8 g/dL

⁃ INR \< 2.0

⁃ Calculated creatinine clearance \> 40 mL/min as determined by Cockcroft-Gault (using actual body weight)

• Males:

⁃ -Creatinine CL (mL/min) = Weight (kg) x (140 - Age) 72 x serum creatinine (mg/dL)

• Females:

⁃ -Creatinine CL (mL/min) = Weight (kg) x (140 - Age) x 0.85 72 x serum creatinine (mg/dL)

• Ability to understand and the willingness to sign a written informed consent document

• Female subjects must be either of non-reproductive potential (i.e., post-menopausal by history: ≥ 50 years old and no menses for ≥1 year without an alternative medical cause; OR history of hysterectomy, OR history of bilateral tubal ligation, OR history of bilateral oophorectomy) or must have a negative serum pregnancy test upon study entry.

• Willing and able to comply with the protocol for the duration of the study including undergoing treatment and scheduled visits and examinations with follow up