This single-center prospective observational cohort study aims to evaluate the predictive value of peripheral blood-based biomarkers for treatment response in patients with hepatocellular carcinoma (HCC) receiving first-line atezolizumab plus bevacizumab (T+A) therapy. Residual peripheral blood samples obtained during routine clinical testing will be analyzed without additional blood draws. The study hypothesizes that baseline and longitudinal peripheral blood biomarkers are associated with treatment response and can be used to identify patients more likely to benefit from T+A therapy. Treatment response will be evaluated based on the best overall response (BOR) during treatment. The primary efficacy assessment will be performed according to RECIST 1.1, while modified RECIST (mRECIST) will be used as a supportive assessment. Predictive models based on peripheral blood biomarkers will be developed using RECIST 1.1-defined treatment response as the primary analysis, with mRECIST used for supportive and sensitivity analyses.