Maximal Standardized Uptake Value on FDG-PET Is Correlated With Cyclooxygenase-2 Expression in Patients With Lung Adenocarcinoma

Abstract

Cyclooxygenase-2 (COX-2) is constitutively overexpressed in a variety of epithelial malignancies and is usually associated with a poor prognosis. Fluorodeoxyglucose positron emission tomography (FDG-PET) has become an important tool for the diagnosis and staging of non-small-cell lung cancer. The maximal standardized uptake values (SUVmax) of primary tumors on FDG-PET have been shown to be correlated with some clinicopathologic factors. In this study, we investigated the prediction of intratumoral COX-2 expression by FDG-PET in cases of lung adenocarcinoma. We conducted a retrospective review of the data of 60 patients with lung adenocarcinoma measuring less than 3 cm in diameter. Immunohistochemical staining for COX-2 and other biological factors that might influence cancer progression was performed, and the correlations of the selective tumor marker expression with the SUVmax were evaluated. A significant correlation was observed between the SUVmax and the expressions of COX-2, Ki-67, and vascular endothelial growth factor (VEGF). Multiple stepwise regression analysis revealed significant relationships between the SUVmax and the expression of COX-2 (p<0.001) and Ki-67 (p=0.016). Of the 2, COX-2 expression was the stronger determinant of the SUVmax, which increased in proportion to the score for COX-2 expression. The recurrence-free survival of patients with elevated COX-2 expression was significantly worse than that of patients not showing COX-2 expression. The expression of COX-2 in primary tumors is as strongly correlated with a worse clinical outcome as is increased FDG uptake in cases of lung adenocarcinoma. These findings indicate that the SUVmax of primary tumors might reflect the biological malignant potential in lung adenocarcinomas.