18F-FDG PET/CT of advanced gastric carcinoma and association of HER2 expression with standardized uptake value

Objective(s): Expression of HER2 in gastric carcinoma has direct prognostic and therapeutic implications in patient management. The aim of this study is to determine whether a relationship exists between standardized uptake value (SUV) and expression of HER2 in advanced gastric carcinoma. Methods: We analyzed the 18F-FDG PET/CT results of 109 patients that underwent gastrectomy for advanced gastric carcinoma. The 18F-FDG PET/CT imaging was requested at the initial staging before surgery. The examinations were evaluated semi-quantitatively, with calculation of maximum standardized uptake values (SUVmax). The clinicopathologic factors, including HER2 overexpression, were determined from tissue obtained from the primary tumor. Metabolic and clincopathologic parameters were correlated using a t-test, one way ANOVA and chi-square test. Results: Immunohistochemically, 26 patients (23.8%) showed HER2 overexpression. This overexpression was significantly associated with high SUV level (P=0.02). The SUV level was significantly correlated with tumor size (P=0.02) and differentiation (P<0.001), and Lauren histologic type (P=0.04). Multivariate analysis showed HER2 overexpression, large tumor size, and differentiation (P=0.022, P=0.002, P<0.001) were significantly correlated with the high level of SUV in advanced gastric carcinoma. No association was found between SUV and T stage and lymph node metastasis. A receiver-operating characteristic curve demonstrated a SUVmax of 3.5 to be the optimal cutoff for predicting HER2 overexpression (sensitivity; 76.9%, specificity; 60.2%). Conclusion: An association exists between high SUV and HER2 overexpression and 18F-FDG PET/CT could be a useful tool to predict the biological characteristics of gastric carcinoma.