AI-assisted ascites volumetry for prognostic stratification in HCC treated with Atezolizumab/Bevacizumab.

PURPOSE: Portal hypertension-related parameters are known to have important prognostic implications in patients with hepatocellular carcinoma (HCC). Ascites has consistently been associated with impaired outcomes. However, the prognostic relevance of quantified ascites volume in patients undergoing Atezolizumab/Bevacizumab remains unclear. METHODS: 90 patients with HCC treated with Atezolizumab/Bevacizumab between 2020 and 2024 were retrospectively included. Ascites was assessed on baseline contrast-enhanced CT imaging using AI-based pre-segmentation followed by manual correction to quantify ascites volume. Overall survival (OS) was analyzed using Kaplan-Meier analysis and Cox regression. Ascites volume was analyzed both as a continuous variable and using predefined volumetric cutoffs (< 613.5 mL and ≥ 613.5 mL). RESULTS: Ascites was present in 39% of patients, with a median ascites volume of 344 mL (IQR 29-929). When analyzed as a continuous variable, ascites volume was significantly associated with impaired OS in univariate analysis (Hazard Ratio (HR) 2.88, p < 0.001) but not after multivariate adjustment (p = 0.214). Stratification by ascites volume revealed a stepwise reduction in OS, with patients without ascites showing the best survival, followed by patients with low-volume ascites (< 613.5 ml), and patients with high-volume ascites (≥ 613.5 ml) demonstrating the poorest outcomes (log-rank p < 0.001). In multivariate analysis, high-volume ascites remained independently associated with impaired OS (HR 4.01, p < 0.001), whereas low-volume ascites did not. CONCLUSION: Ascites volume showed a threshold-dependent prognostic effect in patients with HCC treated with Atezolizumab/Bevacizumab. Volumetric staging identifies high-volume ascites as an independent marker of poor outcome and may provide more clinically relevant risk stratification than binary ascites assessment. CLINICAL TRIAL NUMBER: Not applicable.