title: Protection from right- and left-sided colorectal neoplasms after colonoscopy: population-based study.
abstract: BACKGROUND
  Colonoscopy is used for early detection and prevention of colorectal cancer, but evidence on the magnitude of overall protection and protection according to anatomical site through colonoscopy performed in the community setting is sparse. We assessed whether receiving a colonoscopy in the preceding 10-year period, compared with no colonoscopy, was associated with prevalence of advanced colorectal neoplasms (defined as cancers or advanced adenomas) at various anatomical sites.
  
  
  METHODS
  A statewide cross-sectional study was conducted among 3287 participants in screening colonoscopy between May 1, 2005, and December 31, 2007, from the state of Saarland in Germany who were aged 55 years or older. Prevalence of advanced colorectal neoplasms was ascertained by screening colonoscopy and histopathologic examination of any polyps excised. Previous colonoscopy history was obtained by standardized questionnaire, and its association with prevalence of advanced colorectal neoplasms was estimated, after adjustment for potential confounding factors by log-binomial regression.
  
  
  RESULTS
  Advanced colorectal neoplasms were detected in 308 (11.4%) of the 2701 participants with no previous colonoscopy compared with 36 (6.1%) of the 586 participants who had undergone colonoscopy within the preceding 10 years. After adjustment, overall and site-specific adjusted prevalence ratios for previous colonoscopy in the previous 10-year period were as follows: overall, 0.52 (95% confidence interval [CI] = 0.37 to 0.73); cecum and ascending colon, 0.99 (95% CI = 0.50 to 1.97); hepatic flexure and transverse colon, 1.21 (95% CI = 0.60 to 2.42); right-sided colon combined (cecum to transverse colon), 1.05 (95% CI = 0.63 to 1.76); splenic flexure and descending colon, 0.36 (95% CI = 0.16 to 0.82); sigmoid colon, 0.29 (95% CI = 0.16 to 0.53); rectum, 0.07 (95% CI = 0.02 to 0.40); left colon and rectum combined (splenic flexure to rectum, referred to as left-sided elsewhere), 0.33 (95% CI = 0.21 to 0.53).
  
  
  CONCLUSIONS
  Prevalence of left-sided advanced colorectal neoplasms, but not right-sided advanced neoplasms, was strongly reduced within a 10-year period after colonoscopy, even in the community setting.
authors.affiliation: Division of Clinical Epidemiology and Aging Research, German Cancer Research Center, Bergheimer Str. 20, D-69115 Heidelberg, Germany. h.brenner@dkfz-heidelberg.de
authors.forename: Hermann
authors.initials: H
authors.lastname: Brenner
authors.forename: Michael
authors.initials: M
authors.lastname: Hoffmeister
authors.forename: Volker
authors.initials: V
authors.lastname: Arndt
authors.forename: Christa
authors.initials: C
authors.lastname: Stegmaier
authors.forename: Lutz
authors.initials: L
authors.lastname: Altenhofen
authors.forename: Ulrike
authors.initials: U
authors.lastname: Haug
mesh_terms: D000236:Adenoma / Q000453:epidemiology / Q000517:prevention & control; D002277:Carcinoma / Q000453:epidemiology / Q000517:prevention & control; D003113:Colonoscopy / Q000592:standards / Q000706:statistics & numerical data; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000453:epidemiology* / Q000401:mortality / Q000473:pathology / Q000517:prevention & control*; D015986:Confounding Factors, Epidemiologic; D003430:Cross-Sectional Studies; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D011159:Population Surveillance; D015995:Prevalence; D012044:Regression Analysis; D018570:Risk Assessment; D012307:Risk Factors; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires