OBJECTIVES: Radical resection combined with prophylactic hyperthermic intraperitoneal chemotherapy (p-HIPEC) is a promising treatment for locally advanced gastric cancer (LAGC), though factors influencing its long-term benefits remain unclear. This study aimed to assess the impact of computed tomography (CT)-based body composition parameters on survival in patients undergoing this combination treatment, exploring nutritional factors affecting long-term survival and developing a prognostic model. METHODS: We retrospectively analyzed clinical and CT data from 230 patients with LAGC who underwent radical resection with p-HIPEC between January 2017 and December 2020. Cox regression and Kaplan-Meier analysis were used to identify independent risk factors, and nomograms were constructed based on significant predictors. The models' accuracy was evaluated using receiver operating characteristic (ROC) curves and calibration plots. RESULTS: Of the 230 patients, the 3-year survival rate was 56.1%, with a median overall survival of 49.7 months. Multivariate analysis identified sarcopenia (hazard ratio [HR], 3.078
p <
0.001), low subcutaneous adipose tissue index (HR, 1.739
p = 0.002), high visceral-to-subcutaneous adipose tissue ratio (HR, 1.746
p = 0.002), pT stage (p <
0.001), pN stage (N3: p = 0.004
N2: p = 0.049), and vascular invasion (p <
0.001) as independent risk factors for poor survival. Nomograms incorporating body composition and tumor features predicted 1-, 3-, and 5-year overall survival with high accuracy (AUC >
0.7). CONCLUSIONS: Body composition and tumor characteristics are independent predictors of overall survival in LAGC patients. Nomograms integrating these factors provide reliable prognostic predictions.