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Evaluation of Colon Cancer–Specific Antigen 2 as a Potential Serum Marker for Colorectal Cancer

Authors' Affiliations: ¹ The Brady Urological Institute and ² Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland; and ³ Division of Gastroenterology, Hepatology, and Nutrition and ⁴ Department of Epidemiology, University of Pittsburgh and the University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania

Requests for reprints: Robert H. Getzenberg, The Brady Urological Institute, Johns Hopkins Hospital, Marburg 121, 600 North Wolfe Street, Baltimore, MD 21287. Phone: 410-502-3137; Fax: 410-502-9336; E-mail: rgetzen1{at}jhmi.edu.

Purpose: A blood test to detect colon cancer at a preventable stage would represent a major advancement. We have previously identified colon cancer–specific markers using focused proteomics analysis of nuclear structural proteins. Two of these markers, colon cancer–specific antigen (CCSA)-3 and CCSA-4, have been developed into blood-based markers that are able to distinguish individuals with colorectal cancer from those without. CCSA-2 is a distinct novel colon cancer marker identified using focused proteomics.

Experimental Design: Using an indirect ELISA on serum samples obtained from two institutions, we evaluated CCSA-2 as a serum-based colon cancer marker. A total of 111 serum samples from individuals who underwent colonoscopy and were subsequently diagnosed as either being normal or having hyperplastic polyps, nonadvanced adenomas, advanced adenomas, and colorectal cancer were evaluated. A diverse control population that consisted of 125 serum samples was also included in this study.

Results: Receiver operating characteristic analyses were used to measure the sensitivity and specificity of CCSA-2. CCSA-2 at a cutoff of 10.8 µg/mL has overall specificity of 78.4% [95% confidence interval (95% CI), 67.3-87.1%] and sensitivity of 97.3% (95% CI, 85.8-99.5%) in separating individuals with advanced adenomas and colorectal cancer from normal, hyperplastic, and nonadvanced adenoma populations. The receiver operating characteristic curve for CCSA-2 has an area under the curve of 0.90 (95% CI, 0.83-0.95).

Conclusion: Our initial study shows that CCSA-2 is a potential serum-based marker for colon cancer detection with high sensitivity and specificity.