ABSTRACT
Objective To evaluate the prognostic significance of carbonic anhydrase IX (CA IX) expression in patients with clear cell renal cell carcinoma (ccRCC). Methods CA IX expression in a cohort of 120 patients with ccRCC was evaluated by P-V immunohistochemistry with a rabbit CA IX polyclonal antibody. Twenty-five normal kidney tissues were used as a control. The relationship between CA IX expression and prognosis was analyzed by univariate and multiple-factor analysis (Cox regression model). The primary end point was cancer specific survival. Results One hundred and twelve (93.3%) patients were followed up with the median follow-up time of 45 months (range, 6 to 94 months). Seventy-five patients survived without evidence of tumor recurrence, 3 patients survived with tumor recurrence, and 34 patients died, 28 of the 34 died of cancer. CA IX expression was negative in all normal renal tissue. High CA IX expression was observed in 89 (74.2%) patients, among which 82 patients were followed up, and the disease free survival was 75.6% (62/82). Two (2.4%) patients survived with tumor recurrence, and 18 (22.0%) patients died, of which 13 (15.9%) died of cancer. Tumor recurrence and (or) metastasis occurred in 9 (11.0%) patients, with a median survival of 92 months in this high expression group. Low CA IX expression was observed in 31 (25.8%) patients, among which 30 patients were followed up, and the disease free survival was 43.3% (13/30). One (3.3%) patient survived with tumor recurrence, and 16 (53.3%) patients died, of which 15 (50.0%) died of cancer. Tumor recurrence and (or) metastasis occurred in 8 (26.7%) patients with a median survival of 53 months in this low expression group. Cancer specific survival between CA IX high expression group and low expression group was significantly different (P=0.000, χ2=15.950), and tumor relapse and (or) metastasis rates were significantly different (P=0.040, χ2=4.200). The 1, 3, 5 and 7 year cancer specific survival rates were 95.2%, 83.9%, 81.2% and 78.2% respectively in the high CA IX expression group, and 89.5%, 63.9%, 46.8% and 40.1% respectively in the low expression group. Multivariate analysis with Cox regression model showed that CA IX expression was a prognostic factor (RR=0.186). Conclusions High CA IX expression is negatively correlated with postoperative mortality, relapse and (or) metastasis in ccRCC. CA IX expression could be used as a prognostic biomarker in ccRCC.