Study to Evaluate the Efficacy and Safety of Atezolizumab and Bevacizumab as Neoadjuvant Plus Adjuvant Treatment in HCC

Inclusion Criteria: 1. Signed Informed Consent Form. 2. Age ≥ 18 years at the time of signing Informed Consent Form. 3. Ability to fully comply with the protocol, in the investigator's judgment. 4. Diagnosis of HCC confirmed by histology. 5. HCC that is amenable to R0 surgical resection with curative intent in the opinion of the surgeons and oncologists or hepatologists involved in the care of the participant. 6. HCC at high-risk of recurrence defined by either multifocality, large tumor diameter (\>5cm), AFP (alpha-fetoprotein) ≥400ng/mL, poor tumor differentiation, or the presence of microvascular invasion. \- For patients with tumors between 3-5 cm, a predefined nomogram will be applied, indicating a high prevalence of microvascular invasion with a score \>200 points. (Lie et al., 2016). 7. Measurable disease (at least one target lesion) according to RECIST v1.1 as determined by the investigator. 8. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0. 9. Child-Pugh Class A. 10. No evidence of clinically significant portal hypertension (CSPH) or minor CSPH (HVPG \<12 mmHg) in candidates for minor resection (fewer than 3 segments). (Galle et al., 2018) Clinically significant portal hypertension (CSPH) can be defined either by its gold standard measurement, a hepatic venous pressure gradient (HVPG) ≥10 mmHg, or by the presence of surrogate markers such as a platelet count \<100,000 × 10³/µL combined with splenomegaly. 11. Willing to undergo a tumor biopsy at screening visit. \- Baseline tumor tissue samples will be collected from all participants by means of a core-needle biopsy performed at study entry. A minimum of two core-needle biopsies are required. If a fresh biopsy is not deemed feasible by the investigator, archival tumor tissue may be submitted, provided the tissue was obtained from a biopsy performed within 3 months prior to enrollment and the patient has not received any anti-cancer therapy, including locoregional liver-directed therapy, since the time of the biopsy. Tumor and normal adjacent tissue specimen will be collected at surgery as fresh snap-frozen and formalin-fixed, paraffin-embedded (FFPE) format. FFPE tissue blocks are preferred, or a minimum of 20 slides must be submitted. 12. No prior locoregional or systemic treatment for HCC. 13. Adequate hematologic and end-organ function, defined by the following laboratory test results: * ANC ≥ 1.5 × 109/L (1500/µL) without granulocyte colony-stimulating factor (G-CSF) support. * Lymphocyte count ≥ 0.5 × 109/L (500/µL). * Platelet count ≥ 75 × 109/L (75,000/µL) without transfusion. * Hemoglobin ≥ 90 g/L (9.0 g/dL) without transfusion. Participants must not have required transfusion during screening or within 2 weeks prior to screening to meet this criterion. * AST, ALT, and ALP ≤ 5 × upper limit of normal (ULN). * Bilirubin ≤ 3 × ULN. * Adequate renal function: creatinine clearance by estimated glomerular filtration rate (eGFR) by Modification of Diet in Renal Disease Study (MDRD) formula ≥ 50 mL/min. Participants with creatinine clearance by estimating eGFR by MDRD formula of ≥ 30 mL/min and ≤ 50 mL/min may be enrolled if renal function was stable for ≥ 28 days prior to randomization. * Albumin ≥ 28 g/L (2.8 g/dL) without transfusion. * For participants not receiving anticoagulation: INR or aPTT ≤ 1.5 × ULN. 14. Documented virology status of hepatitis, as confirmed by screening tests for hepatitis B virus (HBV) and/or hepatitis C virus (HCV): * Patients with active HBV must have HBV DNA \< 500 IU/mL during screening, must have initiated anti-HBV treatment at least 14 days prior treatment initiation, and must be willing to continue anti-HBV treatment during the study (per local standard of care, e.g., entecavir). * Patients with HCV, either with resolved infection (as evidenced by detectable antibody) or chronic infection (as evidenced by detectable HCV RNA), are eligible. * For patients with detectable HCV RNA and for whom HCV treatment is considered appropriate by the investigator, treatment should begin no sooner than 6 months following liver resection consistent with AASLD guidelines. 15. Negative HIV test at screening with the following exception: \- Individuals with a positive HIV test at screening are eligible if they are stable on anti-retroviral therapy, have a CD4 count ≥ 200/mL, and have an undetectable viral load. 16. For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraception. 17. For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraception, and agreement to refrain from donating sperm. Exclusion Criteria: 1. Presence of extrahepatic disease or macrovascular invasion. 2. Known fibrolamellar HCC, sarcomatoid HCC, mixed cholangiocarcinoma and HCC, or other rare variants of HCC. 3. History of hepatic encephalopathy if clinically significant within one year prior to screening. 4. CSPH in candidates for major resection (more than 3 segments). 5. Moderate or severe ascites. 6. Active co-infection with HBV and HCV (defined as detectable HCV RNA plus positive HBV surface antigen or HBV DNA). Patients with a history of HCV infection but who are negative for HCV RNA by Polymerase Chain Reaction (PCR) will be considered non-infected with HCV. 7. Known active co-infection with HBV and hepatitis D viral infection (HDV). 8. Prior treatment with immune checkpoint blockade therapies, including anti-CTLA-4, anti-PD-1, and anti-PD-L1 therapeutic antibodies. 9. Treatment with investigational therapy within 28 days prior to screening. 10. Untreated or incompletely treated esophageal and/or gastric varices with bleeding or that are at high risk for bleeding. Participants must undergo an esophagogastroduodenoscopy (EGD), and all size of varices (small to large) must be assessed and treated per local standard of care prior to enrollment. Participan