Prognostic Value of Primary Tumor and Immune Organ Metabolic Parameters Derived from Pretreatment 18F-FDG PET/CT in Gastric Adenocarcinoma: A Retrospective Survival Analysis

Objective: F-FDG PET/CT), with overall survival in gastric adenocarcinoma. Methods: F-FDG PET/CT were retrospectively evaluated. Maximum standardized uptake value, mean standardized uptake value, metabolic tumor volume, total lesion glycolysis (TLG) and immune-organ SUVs were measured and the ratios calculated. Survival analyses used the Kaplan-Meier method, log-rank test, and Cox regression. Results: There were 91 death events (71.7%); the Kaplan-Meier median overall survival was 16.56 months, with 1-, 3-, and 5-year survival rates of 58.3%, 33.1%, and 28.1%, respectively. No significant independent association with overall survival was demonstrated for any of the primary-tumor or immune-organ PET/CT parameters; the SBR was lower in deceased patients (p=0.041) and showed a non-significant protective trend at the univariate level [hazard ratio (HR)=0.802 per 1 standard deviation (SD); 95% confidence interval (CI) 0.621-1.038; p=0.093)], which was not supported by cut-off-based or multivariable analyses. In the primary multivariable model, distant metastasis independently increased the hazard of death (HR=1.798; 95% CI 1.187-2.723; p=0.006), whereas TLG SLR, and BLR showed no independent significance. In the stage-adjusted model, advanced stage remained independently associated with OS (HR=4.403; p=0.001). Conclusion: In this gastric adenocarcinoma cohort with a high proportion of advanced-stage disease, no independent association with overall survival was demonstrated for any of the evaluated tumor- or immune-organ PET/CT parameters; established clinicopathological factors showed stronger prognostic associations than the PET-derived parameters. The prognostic role of immune organ metabolism in gastric cancer should be evaluated in large prospective studies.