Y-90, Capecitabine, and Atezolizumab for Oligometastatic CRC

Inclusion Criteria: 1. Histologically confirmed diagnosis of colorectal adenocarcinoma 2. Surgically unresectable, liver-isolated or liver-dominant, RECIST measurable, metastatic disease 3. Age ≥18 years at the time of signing informed consent 4. ECOG performance status 0 or 1 5. Progression on 2 or more lines of systemic therapy 6. Agreeable to providing tumor tissue and blood for exploratory correlative analyses 7. Less than 50% of liver volume replaced by metastatic disease (as determined by investigator) 8. Demonstrate adequate organ function as defined in table below (all screening labs should be performed within 14 days of atezolizumab initiation): Hematologic Absolute neutrophil count (ANC) ≥1,500 /mcL or ≥1,200 /mcL for those with benign ethnic neutropenia Absolute Lymphocyte Count (ALC) ≥ 0.5 x 109/L (500/uL) Platelets ≥100,000 / mcL Hemoglobin ≥9 g/dL or ≥5.6 mmol/L within 7 days of assessment. Patient may be transfused or receive EPO to meet this criterion Renal Serum creatinine OR measured or calculated creatinine clearance ≤1.5 X upper limit of normal (ULN) OR (GFR can also be used in place of creatinine or CrCl) ≥60 mL/min for subject with creatinine levels \> 1.5 X institutional ULN Hepatic Serum total bilirubin ≤ 1.5 X ULN OR Direct bilirubin ≤ ULN for subjects with total bilirubin levels \> 1.5 ULN AST (SGOT) and ALT (SGPT) ≤ 5 X ULN Alkaline Phosphatase ≤ 5 X ULN Albumin ≥2.5 mg/dL Coagulation International Normalized Ratio (INR) or Prothrombin Time (PT) Activated Partial Thromboplastin Time (aPTT) ≤1.5 X ULN unless subject is receiving anticoagulant therapy. For patients receiving therapeutic anticoagulation: stable anticoagulant regimen ≤1.5 X ULN unless subject is receiving anticoagulant therapy. For patients receiving therapeutic anticoagulation: stable anticoagulant regimen Creatinine clearance should be calculated per institutional standard. Exceptions can be made for patients with known Gilbert disease (≤ 3X ULN) 9. Female subjects of childbearing potential must be willing to use an adequate method of contraception from the time of the negative pregnancy test until a minimum of 6 months after the last dose of study drug. Effective forms of contraception include abstinence, hormonal contraceptive (injectable or implantable), or intrauterine device in conjunction with a barrier method. Breast feeding subjects must be willing to discontinue at treatment start and for 5 months post-treatment. 10. Male subjects of childbearing potential must agree to use an adequate method of contraception with female partners of childbearing potential including abstinence or condoms plus an additional contraceptive method such as hormonal contraceptive (injectable or implantable), or intrauterine device during the study and for up to 3 months after the last dose of study drug. 11. Ability to understand and the willingness to sign a written informed consent document and to comply with the study protocol procedures Exclusion Criteria: 1. Prior yttrium-90 therapy 2. Prior external beam radiation therapy to the liver 3. Predicted life expectancy of less than 3 months 4. Known mismatch repair deficiency (dMMR), microsatellite instability (MSI-H), or high tumor mutational burden (TMB-H) defined as ≥ 10 mutations per megabase 5. Known metastasis to the peritoneum or central nervous system. Exceptions include subjects with untreated brain metastases ≤ 1 cm, if asymptomatic and not requiring immediate radiation or steroids, and subjects with brain metastases that are treated and stable for 1 month 6. Treatment with investigational therapy within the 28 days of initiation of study treatment 7. Systemic treatment within 14 days or 5 half-lives of the drug (whichever is longer) prior to initiation of study treatment 8. Prior treatment with CD137 agonists or anti-PD1, anti-PD-L1, anti-CTLA4 antibodies 9. A history of or current evidence of any condition (e.g. known deficiency of the enzyme dihydropyrimidine dehydrogenase \[DPD\]), therapy, or laboratory abnormality that might confound the results of the trial, interfere with the subject's participation for the full duration of the trial, or is not in the best interest of the subject to participate, in the opinion of the treating investigator 10. Known New York Heart Association class 3/4 congestive heart failure, left ventricular ejection fraction \<40% (if previously measured), myocardial infarction within 6 months prior to enrollment, unstable angina, or unstable arrhythmia 11. Chronic obstructive pulmonary disease (COPD) requiring oral corticosteroids or chronic oxygen 12. History of autoimmune disease, including, but not limited to myasthenia gravis, myositis, autoimmune hepatitis, idiopathic pulmonary fibrosis, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, antiphospholipid syndrome, granulomatosis with polyangiitis, Guillain-Barré syndrome, multiple sclerosis, vasculitis, or glomerulonephritis, with the exception of: hypothyroidism (on stable dose of thyroid replacement therapy), asthma managed with inhaled medications only; type 1 diabetes mellitus on stable insulin regimen, Sjögren syndrome, immune thrombocytopenia or autoimmune hemolytic anemia that does not require systemic therapy; dermatologic condition (including eczema, psoriasis, lichen simplex chronicus, or vitiligo) with skin manifestations with rash covering \<10% of body surface area and not requiring treatment other than low-potency topical corticosteroids for \>12 months prior to registration 13. Treatment with systemic immunosuppressive medication (including, but not limited to, corticosteroids, cyclophosphamide, azathioprine, methotrexate, thalidomide, and anti-TNF-agents) within 2 weeks prior to initiation of study treatment, or anticipation of need for systemic immunosuppressive medication during study treatment, with the following exceptions: * Patients who received acute, low-dose systemic immunosuppressan