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.