title: Colorectal screening is associated with reduced colorectal cancer risk: a case-control study within the population-based Ontario Familial Colorectal Cancer Registry.
abstract: OBJECTIVE
  This is the first study to evaluate the association between colonic screening and colorectal cancer risk among Canadians.
  
  
  METHODS
  A case-control study was conducted. Cases were diagnosed with cancer of the colorectum, between 1997 and 2000, aged 20 to 74 years, identified through the population-based Ontario Cancer Registry and recruited by the Ontario Familial Colorectal Cancer Registry. Controls were a sex- and age-matched random sample of the population of Ontario. 971 cases and 1944 controls completed questionnaires (including colorectal screening history and many risk factors). Multivariate logistic regression analysis was used to obtain adjusted odds ratios (OR) estimates.
  
  
  RESULTS
  Having had a fecal occult blood screen was associated with reduced colorectal cancer risk (OR=0.76; 95% confidence interval (CI): 0.59, 0.97). Having had a screening sigmoidoscopy was associated with a halving of colorectal cancer risk (OR = 0.52; 95% CI: 0.34, 0.80). Having had a screening colonoscopy did not significantly reduce colorectal cancer risk (OR = 0.69; 95% CI: 0.44, 1.07); however, having had either screening endoscopy was associated with a significant reduction in colorectal cancer risk (OR = 0.62; 95% CI: 0.44, 0.87). Findings differed slightly by anatomic sub-site (proximal and distal colorectum).
  
  
  CONCLUSIONS
  We report a reduction in colorectal cancer risk among persons who underwent colorectal cancer screening; in particular, sigmoidoscopy. Findings are of great importance for the prevention of colorectal cancer.
authors.affiliation: Division of Preventive Oncology, Cancer Care Ontario, 620 University Avenue, M5G 2L7, Ontario, Toronto, Canada. michelle.cotterchio@cancercare.on.ca
authors.forename: Michelle
authors.initials: M
authors.lastname: Cotterchio
authors.forename: Michael
authors.initials: M
authors.lastname: Manno
authors.forename: Neil
authors.initials: N
authors.lastname: Klar
authors.forename: John
authors.initials: J
authors.lastname: McLaughlin
authors.forename: Steven
authors.initials: S
authors.lastname: Gallinger
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology*; D016099:Endoscopy, Gastrointestinal; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D009864:Ontario / Q000453:epidemiology; D012042:Registries; D012307:Risk Factors; D040242:Risk Reduction Behavior