Background: Colorectal cancer (CRC) screening guidelines in the U.S. recommend genetic evaluation for individuals with ≥ 10 cumulative colorectal adenomas, as they are thought to have an increased risk for underlying hereditary CRC syndromes. However, little is known about the prevalence, clinical characteristics, and long-term outcomes of patients with ≥ 10 cumulative adenomas.
Aims: To estimate the proportion of patients in a screening cohort who are found to have ≥ 10 cumulative adenomas, examine the demographic and baseline clinical risk factors associated with having ≥ 10 cumulative adenomas, and describe the prevalence of advanced neoplasia (AN) and CRC in these patients.
Patients and Methods: The CSP 380 cohort comprises 3,121 asymptomatic veterans aged 50-75 from 13 VA sites who underwent a screening colonoscopy from 1994-97 and were followed for 10 years until death or last colonoscopy. Of these 3,121 patients, 3,089 did not have CRC at baseline. We identified patients with ≥ 10 cumulative adenomas and compared baseline factors (gender, race, family history of CRC, age, BMI, tobacco use, and alcohol use) in patients with and without ≥ 10 cumulative adenomas. We then estimated the age to ≥ 10 cumulative adenomas. Finally, we calculated the prevalence of AN (polyp ≥ 1 cm, villous histology, high grade dysplasia, or CRC) in patients with ≥ 10 adenomas and those with 0-9 adenomas.
Results: Ten or more cumulative adenomas were found in 66 (2.1%) of the 3089 patients in a 10-year period. Age 60-69 is the single baseline risk factor associated with this outcome. Of the 3,023 patients with 0-9 cumulative adenomas, 348 (11.5%) developed AN, including 23 (0.8%) with CRC. Of the 66 patients with ≥ 10 adenomas, 42 (63.6%) developed AN, including 2 (3.0%) with CRC.
Conclusion: The prevalence of ≥ 10 cumulative adenomas was 2% in this screening population, with few cases before age 60. Few patients with this outcome, however, develop CRC within a 10-year period. Future work could identify additional risk factors associated with the development of ≥ 10 cumulative adenomas in order to create a risk stratification tool that may lead to the earlier detection of patients at high risk for hereditary CRC syndromes, AN, and CRC.