Prognostic value of carbonic anhydrase IX and Ki-67 expression in squamous cell carcinoma of the tongue

Background: Hypoxia-induced changes may allow tumor cells to survive under sustained hypoxic microenvironments resulting in achievement of more aggressive phenotypes. The purpose of this study is to determine the prognostic relevance of the expression of carbonic anhydrase IX (CA IX), a hypoxia-related protein in surgically resected squamous cell carcinoma of the tongue. We also relate CA IX to Ki-67 expression representing tumor cell proliferation to provide a prognostic model. Methods: We analysed the expression of CA IX and Ki-67 with immunohistochemistry in 60 patients with squamous cell carcinoma of the tongue. Results: The percentage of CA IX-positive tumor cells had a wide variation from 0.0 to 77.5%, and the Ki-67 expression was 1.50-75.1%. High CA IX and Ki-67 expression (>= 10.0% of tumor cells positively stained with CA IX and Ki-67) was associated with a poorer overall survival (P < 0.05). High CA IX and Ki-67 expression showed shorter disease-free survival (DFS), although they are not statistically significant. To make a risk model based on the expression of CA IX and Ki-67, we divided the patients into three groups: high risk (high CA IX and Ki-67), low risk (low CA IX and Ki-67) and intermediate risk (either high CA IX or Ki-67). Being in the high-risk group was found to be an independent prognostic factor for overall survival and DFS in multivariate analysis (P < 0.05). Conclusion: The expression of CA IX and Ki-67 may be useful for predicting prognosis in squamous cell carcinoma of the tongue.