Study to Evaluate Efficacy and Safety of Selective Internal Radiation Therapy Plus Xelox, Bevacizumab and Atezolizumab (Immune Chekpoint Inhibitor) in Patients With Liver-dominant Metastatic Colorectal Cancer

Inclusion Criteria: * Age ≥18 years * Histologically proven mismatch repair proficient metastatic colorectal cancer (pMMR and/or MSS) * Liver-dominant disease with up to 6 extrahepatic lesions (only peritoneal lesions are not allowed) if asymptomatic and without organ dysfunction. * Measurable disease according to RECIST 1.1 * Patient with initially unresectable disease according to the local multidisciplinary team and eligible for radioembolization according to the radiologist's opinion * Tumor volume \< 50 % of total liver volume * No prior oncologic treatment for metastatic disease (i.e. chemotherapy, radiotherapy or investigational drug). Patients may have received adjuvant chemotherapy or (neo) adjuvant radiochemotherapy to the pelvis (tumor of the rectum), but the last dose of chemotherapy/radiotherapy must be administered at least 6 months prior to entry into this study. Analgesic radiotherapy of metastasis is permitted except on hepatic lesions and must be completed at least 14 days before inclusion. * WHO performance status ≤ 1 * Estimated life expectancy ≥ 3 months * Adequate hematological function: with neutrophils ≥ 1,500 /mm3, platelet count ≥ 100,000/mm3, hemoglobin \> 9 g/dL (5,6 mmol/l) * Adequate hepatic function: hepatic transaminases (ASAT and ALAT) ≤ 5 x UNL, total bilirubin ≤ 2 x UNL, alkaline phosphatase ≤ 5 x UNL * Adequate renal function: creatinine clearance ≥ 50 ml/min according MDRD (Modification of Diet in Renal Disease) * Patient affiliated to a social security system Information provided to patient and signature of the informed consent form by patient and the investigator Exclusion Criteria: * Active infection still requiring intravenous antibiotics on the first scheduled day of protocol treatment * Symptomatic or untreated central nervous system metastasis * Medical history of other concomitant or previous malignant disease, except adequately treated in situ carcinoma of the uterine cervix, basal or squamous cell carcinoma of the skin, or cancer in complete remission for ≥ 5 years, * Other malignancy in the 5 years prior to inclusion in the study, except for localized cancer in situ, basal or squamous cell skin cancer * Confirmed peritoneal carcinomatosis (lesions detectable on CT-scan and/or MRI) * Active autoimmune disease or inflammatory bowel disease * Bone marrow allograft or solid organ transplant history * History of idiopathic pulmonary fibrosis, drug-induced pneumonitis or evidence of active pneumonitis on screening chest CT-scan and any severe chronic respiratory insufficiency that the investigator believes would not allow the SIRT to be received safely * Positive tests for HIV or other immunodeficiency syndromes * Severe chronic liver failure, which in the investigator's opinion would not allow SIRT to be received safely * Active hepatitis B or hepatitis C. * Active tuberculosis * Patient with contraindication to angiography and selective hepatic catheterization such as bleeding diathesis or coagulopathy with serious bleeding risk that is not correctable by usual therapy of hemostatic agents. * Patients on anticoagulant therapy different from low-molecular-weight heparin (LMWH) cannot be included (i.e. VKA and NOACs). Relaying these anticoagulants to a LMWH before inclusion is allowed. In addition, it must be possible to stop the LMWH 24 hours before invasive procedures according to the usual recommendations (before the work-up and before the SIRT). * Significant presence of ascites, cirrhosis, portal hypertension, main portal venous tumor involvement or thrombosis on clinical or radiological evaluation Previous radiotherapy in the upper abdominal region (liver or liver vessels in the radiation field) * If primary tumor is non-resected, it must be asymptomatic * Long-term immunosuppressant therapy (patients requiring corticosteroid therapy are eligible if they receive a dose equivalent to no more than 10 mg of prednisone equivalent dose per day, and corticosteroid administration is permitted by a route resulting in minimal systemic exposure (cutaneous, rectal, articular, ocular or inhalation) is authorized) * Partial or complete DPD deficiency * Known hypersensitivity to any components of bevacizumab, Chinese Hamster Ovary cell products or other recombinant human or humanized antibodies and any other contraindications to the use of investigational medicinal products, in particular patients with peripheral sensory neuropathy with functional impairment (see SmPC of oxaliplatin) or in the case of recent or concomitant treatment with brivudine (see SmPC of capecitabine) * QT/QTc interval \> 450 msec for male and \> 470 msec for female at EKC. * K+ \< LLN, Mg²+ \< LLN, Ca²+ \< LLN * Allergy to contrast agents that do not allow radioembolization to be performed * Uncontrolled hypertension (blood pressure \> 140 mm Hg and/or diastolic blood pressure \> 90 mm Hg) * Clinically significant cardiovascular disease, for example cerebrovascular accidents ≤ 6 months prior to the start of study treatment, myocardial infarction ≤ 6 months prior to the start of study treatment, unstable angina, congestive heart failure of NYHA (New York Heart Association Functional Classification) grade 2 or higher, or severe cardiac arrhythmia not controlled by drug therapy or which may interfere with study treatment * Significant vascular disease (e.g. aortic aneurysm requiring surgery or arterial thrombosis) within 6 months prior to initiation of study treatment * Venous thromboembolic disease within 3 months prior to initiation of study treatment * Surgical procedure (including surgical biopsy, any surgical resection, or other major surgery) or significant traumatic injury within 28 days prior to start of study treatment, or planning major surgery during the study. * History of abdominal fistula, gastrointestinal (GI) perforation, intra-abdominal abscess or active GI bleeding within 6 months prior to start of study treatment * Unhealing decaying wound, active ulcer, or untreated bone fracture * Proteinuria ≥ 2+ by urine dipstick unless a 24-hour urine protein \< 1 g of protein is demonstrated * Lack of effective contraception in patients (male and/or female) at risk of reproduction, pregnant or breastfeeding women and women at risk of reproduction who have not had a pregnancy test. * Persons deprived of freedom or under guardianship * Inability to undergo medical follow-up of the study for geographical, social or psychological reasons