Abstract 477: Elevated EVL methylation level in the normal colon mucosa is a potential risk biomarker for developing metachronous polyps

The purpose of this study is to evaluate the use of molecular markers for more accurately predicting the individual risk of metachronous polyps or cancer during colonoscopic surveillance. Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related death in the United States. The risk of CRC varies among people; individuals who develop adenomas are at heightened risk of forming metachronous adenomas and interval cancer, compared to those without a personal history of adenoma or CRC. Yet, even in these high risk individuals, only 25-30% will develop subsequent adenomas. To date, few studies have evaluated the use of molecular markers for predicting the risk of metachronous lesions. We have demonstrated that aberrantly methylated mir342/EVL is present at a higher frequency in the normal colon of people with CRC compared to people with no colon cancer or polyps, suggesting it may indicate a field cancerization process. Further, we developed an ultra-sensitive quantitative Methylation-specific ddPCR (MS-ddPCR) assay to accurately determine the level of rare EVL methylation in the normal colon mucosa. To investigate the correlation of EVL methylation in normal mucosa and the risk of developing polyps during the follow-up colonoscopy, we conducted a retrospective cohort study (N=136 subjects) and EVL methylation status was determined in normal colon mucosa samples from these subjects. Among them, 71 subjects had polyps detected within 12 years of the index colonoscopy, and 11 subjects were polyp-free at all subsequent colonoscopic exams done within 8-16 years of the index colonoscopy (54 subjects did not meet the criteria for follow up, so were excluded from the following analysis). Applying the standard Inverse Probability Weighted Logistic Regression (IPWLR) model, we found that higher level of EVL methylation in the normal colon mucosa at the time of the index colonoscopy (which was when the tissue sample was collected) indicated an increased risk of having polyps detected within 12 years, compared to subjects with no polyps detected by colonoscopy done within 8-16 years (Odds Ratio (95% CI) = 4.35 (1.14, 16.60); p-value = 0.0317). Our results suggest that EVL methylation level in the normal colon mucosa can be used as a risk biomarker for metachronous adenomas. Citation Format: Ming Yu, Ting Wang, Kelly T. Carter, Kelsey Baker, Mary W. Redman, Kathy Vickers, Lynda Ann Dzubinski, Robert E. Schoen, William M. Grady. Elevated EVL methylation level in the normal colon mucosa is a potential risk biomarker for developing metachronous polyps [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 477.