The Prognostic Significance of Preoperative Staging 18F-FDG PET/MRI Findings in Gastric Cancer Patients Undergoing Gastrectomy.

Abstract

Objective: The aim of this retrospective study was to investigate the prognostic value of preoperative findings on ¹⁸F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (¹⁸F-FDG PET/MRI) in gastric cancer (GC) patients who underwent total or subtotal gastrectomy.

Methods: Patients with GC who underwent pretreatment staging with ¹⁸F-FDG PET/MRI and subsequently underwent total or subtotal gastrectomy were included in the study. Demographic and clinicopathologic features of patients were recorded. The maximum wall thickness of gastric tumors, the minimum apparent diffusion coefficient (ADC_min), the total number and maximum standard uptake values (SUV_max) of ¹⁸F-FDG-positive lymph nodes, the short-axis diameter of the largest lymph node, and the tumor SUV_max-to-liver SUV_mean ratio on ¹⁸F-FDG PET/MRI were recorded. Predictors of mortality were evaluated using Cox proportional hazards regression models. Survival analysis was conducted using the Kaplan-Meier method.

Results: Seventy-eight patients with GC who underwent gastrectomy were included in the study. The median follow-up duration was 23.9 months (interquartile range: 33.4); 39 patients (50.0%) died during follow-up. In the multivariate analysis, the tumor SUV_max/liver SUV_mean ratio (p=0.002) and tumor histopathologic group (p<0.001) were identified as independent predictors of overall survival. The mean overall survival was 42.7 months [95% confidence interval (CI): 35.8-49.6]. The mean overall survival in the signet-ring cell carcinoma/other subtypes group (31.4 months; 95% CI: 22.3-40.4) was significantly shorter than that in the adenocarcinoma group (49.2 months; 95% CI: 40.3-58.2) (p=0.019). Patients with a tumor SUV_max/liver SUV_mean ratio greater than 2.6 on ¹⁸F-FDG PET/MRI (35.7 months; 95% CI: 27.6-43.7) had a shorter overall survival than those with a ratio lower than 2.6 (57.1 months; 95% CI: 46.5-67.7) (p=0.005).

Conclusion: The tumor SUV_max-to-liver SUV_mean ratio may serve as a robust imaging biomarker for prognosis and for determining histopathologic subtype in GC patients who underwent total or subtotal gastrectomy.