A Phase 1 Study of Combined Y-90 Selective Internal Radiation Therapy (Y-90 SIRT) and Stereotactic Body Radiation Therapy (SBRT) in Hepatic Malignancy.

Inclusion Criteria: * Diagnosis of unresectable hepatocellular carcinoma or metastatic liver cancer. Hepatocellular carcinoma is defined as having at least one of the following: * Biopsy proven hepatocellular carcinoma (HCC); or * A discrete hepatic tumor(s) as defined by the Barcelona imaging criteria. Metastatic liver cancer is defined as having: o pathological confirmation of any metastatic disease with a new or enlarging liver lesion consistent with metastases. The targeted lesion does not need to be biopsied if the patient has a known history of metastatic disease * Patients must not have known untreated or progressive disease outside of the liver * At least one lesion \>2 cm diameter or 4 cc volume * Patients must have a life expectancy of at least 6 months. * Patients must be 18 years of age or older * All men, as well as women of childbearing potential, must agree to use effective contraception throughout the study and for 90 days following treatment. * Patients must understand and be willing to sign an informed consent form approved for this purpose by the Institutional Review Board (IRB) of the University of Michigan Medical Center indicating that they are aware of the investigational aspects of the treatment and the potential risks. Exclusion Criteria: * Inability to lie still for imaging studies (e.g. PET/CT) * Pregnancy or nursing females or refusal to use birth control in patients capable of reproduction. * Patients with known allergy or contraindication to intravenous iodinated contrast agents * Patients with an allergy or contraindication to MRI on MRI contrast (Eovist or Gadolinium) * Contraindication to Theraspheres * Tc-99m macroaggregated albumin (MAA) hepatic arterial perfusion scintigraphy showing any deposition to the gastrointestinal tract that may not be corrected by angiographic techniques * Shunting of blood to the lungs that could result in delivery of greater than 30 Gy to the lungs. * Hepatic artery catheterization contraindication; such as patients with vascular abnormalities or bleeding diathesis; * Bilirubin \>2.0 at baseline * Occlusion of the main portal vein * Contraindication to radiation therapy * Note: Patients who have an increase in bilirubin \>1.0 from the time of Y90 to SBRT or his/her bilirubin goes above 2.5 after Y90 will not be eligible for SBRT.