title: Relationship between frequency of surveillance  colonoscopy and colorectal cancer prevention.
abstract: OBJECTIVE
  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.
authors.forename: Takuji
authors.initials: T
authors.lastname: Kawamura
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Oda
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Murakami
authors.forename: Kiyonori
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Koji
authors.initials: K
authors.lastname: Matsuda
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Kida
authors.forename: Kiyohito
authors.initials: K
authors.lastname: Tanaka
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Kawahara
authors.forename: Wasaburo
authors.initials: W
authors.lastname: Koizumi
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Yasuda
authors.forename: Hisao
authors.initials: H
authors.lastname: Tajiri
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D016022:Case-Control Studies; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D003110:Colonic Neoplasms / Q000473:pathology* / Q000517:prevention & control*; D003111:Colonic Polyps / Q000175:diagnosis / Q000473:pathology*; D003113:Colonoscopy / Q000379:methods / Q000706:statistics & numerical data*; D055088:Early Detection of Cancer / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007564:Japan; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D015999:Multivariate Analysis; D009361:Neoplasm Invasiveness / Q000473:pathology; D009367:Neoplasm Staging; D016017:Odds Ratio; D018570:Risk Assessment; D012737:Sex Factors; D013997:Time Factors