Predictive value of 18F-FDG PET/CT metabolic parameters for gastric cancer patients’ microsatellite instability status

This study is to investigate the feasibility of using the 18F fluorodeoxyglucose (18F-FDG) positron emission tomography / computed tomography (PET/CT) metabolic parameters to predict the MSI status of gastric cancer (GC) patients. Patients with GC who underwent 18F-FDG PET/CT before surgery from January 2021 to June 2022 were retrospectively analyzed. Calculate and record the 18F-FDG PET/CT metabolic parameters of primary gastric cancer lesions, including maximum, peak and average standardized uptake values (SUVmax, SUVpeak, and SUVmean), as well as metabolic tumor volume (MTV) and total lesion glycolysis (TLG). The status of MSI was determined by immunohistochemical assay. The differences of quantitative parameters between MSI and microsatellite stability (MSS) groups were evaluated, and the prediction performance of metabolic parameters was analyzed by using subject operating characteristic (ROC) analysis and area under ROC curve (AUC). 62 patients (44 males and 18 females; age range 30-81 years-old, median age 65.5 years-old) were finally included. There were 20 patients in MSI group and 42 patients in MSS group. MTV30%, MTV40%, MTV50% and MTV60%, as well as TLG40% showed significant differences between the two groups (all P values <0.05), within which MTV40% demonstrated the highest AUC value [0.825, 95% confidence interval (CI): 0.703-0.947] in predicting MSI, the cutoff value was 44.1. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy value were 66.7%, 97.6%, 86.7%, 85.1%, and 85.5%, respectively. In multiple logistic regression analysis, MTV40% was an important predictor of MSI. 18F-FDG PET/CT metabolic parameters could predict the preoperative GC MSI status, and MTV40%shows the highest predictive efficiency. 18F-FDG PET/CT imaging might be used as a non-invasive tool to guide the immunotherapy and individualized treatment of GC patients.