This study aimed to investigate whether the expression of carbonic anhydrase IX (CAIX) is associated with the expression of vascular endothelial growth factor (VEGF) and whether the co-expression of the two correlates with survival outcome in clear cell renal cell carcinoma (ccRCC). The expression of CAIX and VEGF was evaluated immunohistochemically in 122 paraffin-embedded ccRCC specimens. The clinical significance of these markers in relation to disease-specific survival (DSS) was analyzed. Patients with a low expression of CAIX had a significantly worse prognoses than those with a high expression (p=0.0005). Inversely, patients with a high expression of VEGF had a significantly worse prognoses than the patients with a low expression (p=0.0030). Furthermore, CAIX expression significantly stratified the DSS of patients with high-stage (p=0.0001), high-grade (p=0.0392), low-grade (p=0.0273), metastasis (p=0.0034), no metastasis (p=0.0303) and ECOG-PS=0 (p=0.0003). VEGF expression significantly predicted the survival of patients with low-grade (p=0.0003), high-stage (p=0.0401) and ECOG-PS=0 (p=0.0063). A multivariate Cox regression analysis showed that tumor stage (p=0.0054), metastasis (p=0.0193), ECOG-PS (p=0.0065) and CAIX expression (p=0.0001) were independent prognostic factors of DSS. Since CAIX and VEGF expression correlated inversely (p=0.0032), the prognostic value of the co-expression of CAIX-VEGF was evaluated. Multivariate analysis revealed that the co-expression was an independent prognostic factor of DSS (p=0.0002). In addition, the co-expression was able to stratify DSS into three risk groups: high-risk, intermediate-risk and low-risk (p<0.0001). In patients with ccRCC, CAIX and VEGF expression correlated inversely. Independent expression of CAIX and a co-expression of CAIX-VEGF were found to be independent predictors of DSS. Furthermore, the co-expression data for CAIX-VEGF provide more accurate prognostic information than the individual data. This information may be useful for survival prediction and risk stratification of patients with ccRCC.

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