Objectives: To present extended follow-up on a cohort of patients with renal cortical tumors treated with partial or radical nephrectomy and preoperatively assess for carbonic anhydrase 9 tumor marker expression in the peripheral blood. Methods: All patients were originally enrolled in an institutional review board-approved study assessing the role of a reverse-transcriptase polymerase chain reaction peripheral blood assay designed to detect the tumor-specific gene carbonic anhydrase-9 (CA9). A total of 41 patients with renal cortical tumors confined to the kidney were enrolled at a single institution and assessed preoperatively with peripheral blood test for CA9 expression before undergoing partial or radical nephrectomy. A Kaplan-Meier estimated survival analysis and log-rank test were performed to determine whether detection of peripheral blood cells expressing the CA9 gene influences disease-free and disease-specific survival. Results: The median follow-up was 4.3 years. The median age was 71 years. Of the 41 patients, 26 were men and 15 were women. The estimated 5-year disease-free survival for patients with detectible expression of the CA9 gene in the peripheral blood was 39.5% compared with 88.1% for patients without detection of the CA9 gene (P = 0.048). On bivariate analysis, disease-free survival correlated with histologic type, tumor diameter, and tumor grade. Conclusions: The expression of the tumor-specific marker CA9 in the peripheral blood is associated with decreased disease-free survival in patients with renal cortical tumors. This is the first study reporting on the prognostic value of this peripheral blood-based tumor marker for kidney tumors.
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