Ten or More Cumulative Lifetime Adenomas Are Associated with Increased Risk for Advanced Neoplasia and Colorectal Cancer

Abstract

Background: Colorectal cancer (CRC) screening guidelines recommend frequent colonoscopies and consideration of genetic testing in individuals with ≥10 cumulative adenomas. However, it is unclear how these guidelines apply to routine practice.

Aims: We estimated the proportion of participants found to have ≥10 cumulative adenomas in a screening population and described their outcomes of advanced neoplasia (AN), CRC, and extra-colonic malignancy.

Methods: We performed a secondary analysis of VA CSP#380, which includes 3121 veterans aged 50-75 who were followed up to 10 years after screening colonoscopy. We calculated the cumulative risk of ≥10 cumulative adenomas by Kaplan-Meier method. We compared baseline risk factors in those with and without ≥10 cumulative adenomas as well as the risk for AN (adenoma ≥1 cm, villous adenoma or high-grade dysplasia, or CRC) and extra-colonic malignancy by multivariate logistic regression.

Results: The cumulative risk of ≥10 cumulative adenomas over 10.5 years was 6.51% (95% CI 4.38%-9.62%). Age 60-69 or 70-75 at baseline colonoscopy was the only factors associated with the finding of ≥10 cumulative adenomas. Compared to those with 0-9 cumulative adenomas, participants with ≥10 cumulative adenomas were more likely to have had AN (OR 17.03; 95% CI 9.41-30.84), including CRC (OR 7.00; 95% CI 2.84-17.28), but not extra-colonic malignancies.

Conclusions: Approximately 6.5% of participants in this screening population were found to have ≥10 cumulative adenomas over 10.5 years, which was uncommon before age 60. These participants were found to have AN and CRC significantly more often compared to those with lower cumulative adenomas.

Keywords: Advanced neoplasia; Colonic adenomatous polyposis; Colorectal cancer; Colorectal cancer screening; Cumulative adenoma counts.