title: Reduced risk of colorectal cancer up to 10 years after screening, surveillance, or diagnostic colonoscopy.
abstract: OBJECTIVE
  Data from randomized controlled trials on the effects of screening colonoscopies on colorectal cancer (CRC) incidence and mortality are not available. Observational studies have suggested that colonoscopies strongly reduce the risk of CRC, but there is little specific evidence on the effects of screening colonoscopies.
  
  
  METHODS
  We performed a population-based case-control study of 3148 patients with a first diagnosis of CRC (cases) and 3274 subjects without CRC (controls) from the Rhine-Neckar region of Germany from 2003 to 2010. Detailed information on previous colonoscopy and potential confounding factors was collected by standardized personal interviews. Self-reported information on colonoscopies and their indications was validated by medical records. We used multiple logistic regression to assess the association between colonoscopy conducted for specific indications within the past 10 years and risk of CRC.
  
  
  RESULTS
  A history of colonoscopy was associated with a reduced subsequent risk of CRC, independently of the indication for the examination. However, somewhat stronger associations were found for examinations with screening indications (adjusted odds ratio [OR] 0.09, 95% confidence interval [CI] 0.07-0.13) than for examinations with diagnostic indications, such as positive fecal occult blood test result (OR, 0.33; 95% CI, 0.19-0.57), surveillance after a preceding colonoscopy (OR, 0.33; 95% CI, 0.24-0.45), rectal bleeding (OR, 0.28; 95% CI, 0.20-0.40), abdominal symptoms (OR, 0.15; 95% CI, 0.10-0.21), or other (OR, 0.21; 95% CI, 0.14-0.30). Colonoscopy was also associated with a reduced risk of cancer in the right colon, regardless of the indication, although to a smaller extent than for other areas of the colon (OR for screening colonoscopy, 0.22; 95% CI, 0.14-0.33).
  
  
  CONCLUSIONS
  In a population-based case-control study, the risk of CRC was strongly reduced up to 10 years after colonoscopy for any indication. Risk was particularly low after screening colonoscopy, even for cancer in the right colon.
authors.affiliation: Division of Clinical Epidemiology and Aging Research, German Cancer Research Center, Heidelberg, Germany; German Cancer Consortium, Heidelberg, Germany. Electronic address: h.brenner@dkfz.de.
authors.forename: Hermann
authors.initials: H
authors.lastname: Brenner
authors.affiliation: Unit of Genetic Epidemiology, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Jenny
authors.initials: J
authors.lastname: Chang-Claude
authors.affiliation: Division of Clinical Epidemiology and Aging Research, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Lina
authors.initials: L
authors.lastname: Jansen
authors.affiliation: Department of General, Visceral and Transplantation Surgery, University of Heidelberg, Heidelberg, Germany.
authors.forename: Phillip
authors.initials: P
authors.lastname: Knebel
authors.affiliation: Division of Clinical Epidemiology and Aging Research, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Stock
authors.affiliation: Division of Clinical Epidemiology and Aging Research, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hoffmeister
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology* / Q000473:pathology; D055088:Early Detection of Cancer; D004522:Educational Status; D062665:Epidemiological Monitoring; D005260:Female; D005858:Germany; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects; D012923:Social Class
keywords: Colonoscopy; Colorectal Cancer; Early Detection; Prevention