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

OBJECTIVES 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 (18)F-FDG PET/CT results of 109 patients that underwent gastrectomy for advanced gastric carcinoma. The (18)F-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 (18)F-FDG PET/CT could be a useful tool to predict the biological characteristics of gastric carcinoma.