Advanced Colonic Neoplasia at Follow-up Colonoscopy According to Risk Components and Adenoma Location at Index Colonoscopy: A Retrospective Study of 1,974 Asymptomatic Koreans

Background/Aims We aimed to estimate the cumulative incidence of advanced colonic neoplasia and analyze the risk factors for advanced colonic neoplasia according to risk components and adenoma location at index colonoscopy. Methods We reviewed 1,974 subjects who underwent a follow-up colonoscopy after a complete screening colonoscopy and the removal of all polyps. We estimated the cumulative incidence of a subsequent advanced neoplasia according to risk groups (normal, low-risk, and high-risk). Risk factors were analyzed by risk components (≥3 adenomas, adenoma ≥1 cm, and villous-type adenoma) and adenoma location. Results Overall, 111 advanced neoplasias (5.6%) were newly diagnosed at the follow-up colonoscopy. The 3-year cumulative incidences of advanced neoplasia were 0.8%, 3.1%, and 10.2% in the normal, low-risk, and high-risk groups, respectively (p<0.0001), and the 5-year cumulative incidences were 2.2%, 8.6%, and 20.2%, respectively (p<0.0001). Age ≥60 years (hazard ratio [HR], 1.78; 95% confidence interval [CI], 1.21 to 2.63), right-sided colonic adenoma (HR, 1.74; 95% CI, 1.13 to 2.66), ≥3 adenomas (HR, 2.00; 95% CI, 1.22 to 3.28), and adenomas ≥1 cm in size (HR, 2.03; 95% CI, 1.20 to 3.44) in the index colonoscopy were independent risk factors for subsequent development of advanced neoplasia. Conclusions Right-sided colonic adenoma, ≥3 adenomas, adenomas ≥1 cm, and age ≥60 years at the index colonoscopy were significant risk factors for advanced neoplasia following a complete screening colonoscopy and removal of all polyps.