Serum carbonic anhydrase IX and its prognostic relevance in vulvar cancer

Therapeutic options in advanced or recurrent vulvar cancer are limited. The identification of new prognostic factors and markers for therapy stratification is therefore highly desirable. Carbonic anhydrase IX (CAIX) is up-regulated in various solid tumors and a promising new target. We therefore determined CAIX serum concentration and its prognostic relevance in correlation to intratumoral CAIX expression in patients with primary vulvar cancer.

Thirty-one serum samples of patients with primary vulvar cancer were prospectively collected before surgery and analyzed for CAIX by enzyme-linked immunosorbent assay. In addition, intratumoral CAIX expression was determined by immunohistochemistry and correlation with serum CAIX and clinicopathological factors, and outcome was analyzed.

Preoperative serum concentration of CAIX ranged between 56 and 879 pg/mL (median, 147 pg/mL; mean, 237.29) and was significantly higher in patients with high intratumoral expression (median, 269 pg/mL vs 126 pg/mL, P = 0.03). High serum CAIX was not associated with any of the analyzed clinicopathological parameters. However, disease-free survival was shorter in patients with high preoperative serum CAIX (above median; P = 0.012). By immunohistochemistry, 26% of the tumors showed a moderate or strong expression of CAIX, whereas 74% showed weak or no expression. High intratumoral expression of CAIX was also associated with unfavorable disease-free survival (P = 0.043).

Carbonic anhydrase IX serum concentration is higher in patients with high intratumoral expression, and elevated preoperative serum values are associated with unfavorable prognosis. Serum CAIX might therefore be an easily assessable marker to stratify patients for adjuvant therapy and potentially monitor response. Carbonic anhydrase IX is differentially expressed in vulvar cancer and potentially associated with negative outcome.