Serum carbonic anhydrase IX during first-line therapy of ovarian cancer

Objective: Carbonic anhydrase IX (CAIX) is primarily involved in maintaining the extracellular pH. It is overexpressed in a variety of tumors including ovarian cancer. To evaluate the potential prognostic and predictive role of serum CAIX for therapy response in ovarian cancer, we analyzed longitudinal serum samples.

Methods: One hundred forty-eight serum samples from 37 patients with primary epithelial ovarian cancer were analyzed. Samples were prospectively collected at 4 time points: (1) before radical surgery, (2) after surgery and before platinum/taxane chemotherapy, (3) during chemotherapy, and (4) after chemotherapy. Serum CAIX was quantified by ELISA and expression in tumor tissue was verified by immunohistochemistry. Correlation with response and clinical outcome as well as the tumor marker CA-125 was analyzed.

Results: Serum concentration of CAIX ranged between 30 and 1687 pg/mL and showed no significant changes during first-line therapy (median level before and after surgery 204 and 198 pg/mL, during and after chemotherapy 175 and 181 pg/mL). There was no association between serum CAIX and progression-free or overall survival. CA-125 decreased significantly after surgery (median serum level before and after surgery 413 and 84 kU/L, p<0.001) and further during and after first-line chemotherapy (median serum levels 21 and 15 kU/L, p<0.001). No intermarker correlation was observed.

Conclusions: CAIX is upregulated in ovarian cancer and serum CAIX could be a marker to stratify patients for therapy response. However, CAIX serum levels did not change significantly during first-line therapy and were not prognostically relevant. Based on the findings of the current study, CAIX cannot be recommended for therapy monitoring in this context.