Non-Invasive Prediction of Colorectal Neoplasia

Overview

Hypothesis:The Adnab-9 antigen is a predictive biomarker in individuals at risk of developing colorectal neoplasia. Study aim is to evaluate the potential of the Adnab-9 monoclonal antibody (MAb) as a marker of cancer risk in a population at increased risk for colorectal cancer (CRC). This marker would be compared to other current and emerging diagnostic methods. 2,800 Veterans would be recruited into the study. In phase 1, candidates would be defined as having increased CRC risk by a short questionnaire. Stool samples would be obtained and a semi-quantitative Adnab-9 antigen assay (ELISA) would be determined. Patients with differing high and low estimations of fecal Adnab-9 would undergo colonoscopy at which time other samples of effluent and colonic mucosa would be taken, and a detailed lifestyle and nutritional questionnaire would be completed. The characteristics of the Adnab-9 fecal test as a diagnostic test would be critically determined using the outcome of the colonoscopic and other test results. The patients will be contacted through the mail and by word of mouth. Informed consent will be obtained before the samples are obtained. The participants are clinically defined as high-risk and therefore screening colonoscopy would be likely performed in any event. A number of assays for Adnab-9 are feasible including slot-blot, Western blot, and ELISA. Other stool studies include conventional fecal occult blood tests (FOBT or FIT) that will be performed in tandem. The investigators therefore began this method of collection and obtained consent from over 2000 patients with a similar overall compliance rate with FOBT screening procedures to that reported previously of approximately 50%. Currently the study is no longer enrolling patients at the Detroit VA and is now finalizing data entry. Another 450 patients to be recruited at the Philadelphia VAMC.

The primary objectives is to test the efficacy of Adnab-9 stool testing in a population at high-risk for colorectal neoplasia and directly compare it to that of the FOBT and secondarily, identify the source of the Adnab-9 antigen to determine influences of diet and environment on its expression. The design is a prospective cross sectional (Part 1) and a case-control longitudinal follow-up study (Part 2) using a brief questionnaire to assess risk for cancer in a total of 2800 Part I patients will be enrolled designed to achieve a database of high risk individuals and measure fecal Adnab-9 levels before a clinically indicated colonoscopy is performed. The patients submit 4 FOBT cards in a routine manner by mail, 3 are used for the FOBT and stool is extracted from the last card for the Adnab-9 ELISA which is reported as OD/5ug protein/well. 100 Part 2 enrollees are then selected on the basis of positive fecal Adnab-9 test candidates matched with a like number of patients with negative stool results who have had their initial colonoscopy and who will have a 5-year follow-up colonoscopy. Detailed Adnab-9 testing (immunohistochemical Adnab-9 binding; blood biomarker estimations and Adnab-9 Western blotting) will be performed on various bodily fluids to perfect the method of testing and completion of the detailed questionnaire to check for reproducibility and interim lifestyle changes in these participants.