Background and aim: The impact of frequent colonoscopy on colorectal cancer (CRC) remains unclear. The present study aimed to determine the relationship between frequency of surveillance colonoscopy and CRC prevention.
Methods: From April 2010 to April 2011, patients who underwent surveillance colonoscopy after screening and polypectomy in four Japanese endoscopy centers were enrolled in this multicenter historical cohort study. Patients were classified into the following two groups according to the findings of past colonoscopy: a low-risk group (no neoplasia or 1-2 cumulative adenomas <10 mm) and an increased-risk group (advanced adenoma or ≥ 3 cumulative adenomas). The relationship between colonoscopy frequency within the previous 5 years and the prevalence of advanced neoplasia in each group was analyzed using multiple logistic regression.
Results: The final analysis included 2391 patients. In the low-risk group, the odds ratios for advanced adenoma in patients undergoing moderately frequent colonoscopy (2-3 times within the previous 5 years), and frequent colonoscopy (≥ 4 times within 5 years) were 0.33 (95% confidence interval [CI], 0.14-0.81) and 0.21 (95% CI, 0.02-1.60), respectively, compared with infrequent colonoscopy (once or not at all within 5 years). In the increased-risk group, the respective odds ratios were 0.48 (95% CI, 0.28-0.83) and 0.28 (95% CI, 0.12-0.64).
Conclusions: Although frequent colonoscopy provides benefits against advanced adenoma, the optimal benefit was achieved at 2-3 times. With very frequent colonoscopy (i.e. ≥ 4 times within 5 years), the additional risk reduction for advanced adenoma was relatively small.