Prognostic Value of 18F-FDG and 18F-FEC Uptake in Hepatocellular Carcinoma Using Contrast-Enhanced Integrated PET/MRI: Correlation with Histology and Survival

Background: Dual-tracer positron emission tomography/magnetic resonance imaging (PET/MRI) using [18F]-fluorodeoxyglucose (18F-FDG) and [18F]-fluoroethylcholine (18F-FEC) may reveal complementary aspects of hepatocellular carcinoma (HCC) biology. This retrospective study evaluates whether PET parameters obtained from 18F-FDG and 18F-FEC correlate with MRI enhancement parameters, tumor histological grade, and survival in patients with HCC. Methods: We retrospectively evaluated 25 patients who underwent integrated PET/MRI. Lesions were analyzed on pre-contrast MRI and at early (3–5 min) and late (20–30 min) post-contrast phases. For 18F-FDG and 18F-FEC, standardized uptake values (SUV maximum, mean, and peak) and metabolic tumor volume were measured, along with lesion size, MRI enhancement ratios, AFP levels, and survival. For patient-level imaging analyses, the largest lesion per patient was defined as the index lesion. Correlation analysis using Spearman’s rank correlation coefficient, Kaplan–Meier analysis, log-rank testing, and exploratory Cox proportional hazards models were performed. Results:18F-FDG SUVmean (index lesion) showed the strongest inverse association with survival (r = −0.61, p = 0.003), followed by SUVpeak (r = −0.50, p = 0.012). 18F-FDG SUVmean differed across tumor grades (G1–G3; p = 0.040), without a consistent trend. In Cox regression, 18F-FDG SUVpeak was significantly associated with shorter overall survival (HR 1.22, 95% CI 1.05–1.42, p = 0.01), whereas SUVmean showed only a borderline association (p = 0.07). When split at the median, SUVmean was also significantly associated with shorter survival (p < 0.001; HR 10.39, 95% CI 2.75–39.3). 18F-FEC parameters were not associated with survival but showed a moderate correlation with AFP levels (r = 0.41, p = 0.01). Dynamic MRI early and delayed enhancement of the index lesion were strongly correlated (r = 0.70, p < 0.001) but not associated with survival. Conclusions: In HCC, 18F-FDG uptake provides prognostic information beyond MRI enhancement and histology, reflecting tumor aggressiveness and independently predicting survival. While 18F-FEC-PET complements lesion characterization and correlates with AFP, it does not show meaningful prognostic value. MRI enhancement parameters were not associated with survival in this cohort. 18F-FDG-based metabolic imaging may improve pre-treatment risk stratification, whereas dual-tracer PET/MRI should be considered a selective, exploratory approach rather than routine imaging.