title: The reduction in colorectal cancer mortality after colonoscopy varies by site of the cancer.
abstract: OBJECTIVE
  There are limited data on mortality from colorectal cancer (CRC) among patients who have received colonoscopy examinations. We sought to determine CRC mortality among persons undergoing colonoscopies compared with the general population.
  
  
  METHODS
  We identified all individuals who had a colonoscopy as their first lower gastrointestinal endoscopy from April 1, 1987, to September 30, 2007 (24,342 men and 30,461 women), based on information from Manitoba's provincial physicians' billing claims database. Patients were followed until March 31, 2008, death, or migration out of the province (310,718 person-years). Individuals less than 50 years of age or more than 80 years of age at the index colonoscopy or those with prior sigmoidoscopy, inflammatory bowel disease, resective colorectal surgery, or CRC were excluded. CRC mortality after the index colonoscopy was compared with that of the general population by standardized mortality ratios (SMRs). Stratified analyses were performed to determine CRC mortality for different age groups at index colonoscopy and sex, duration of follow-up, medical specialty of the endoscopist, and site of CRC.
  
  
  RESULTS
  There was a 29% reduction in overall CRC mortality (SMR, 0.71; 95% confidence interval [CI], 0.61-0.82], a 47% reduction in mortality from distal CRC (SMR, 0.53; 95% CI, 0.42-0.67), and no reduction in mortality from proximal CRC (SMR, 0.94; 95% CI, 0.77-1.17). The reduction in mortality from distal CRC remained significant for follow-up beyond 10 years (SMR, 0.53; 95% CI, 0.31-0.84).
  
  
  CONCLUSIONS
  In Manitoba, colonoscopies significantly reduce mortality from CRC, but the benefit is not uniform for colorectal tumors that arise in different areas of the colon.
authors.affiliation: Internal Medicine and University of Manitoba IBD Clinical and Research Centre, Winnipeg, Manitoba, Canada. singh@cc.umanitoba.ca
authors.forename: Harminder
authors.initials: H
authors.lastname: Singh
authors.forename: Zoann
authors.initials: Z
authors.lastname: Nugent
authors.forename: Alain A
authors.initials: AA
authors.lastname: Demers
authors.forename: Erich V
authors.initials: EV
authors.lastname: Kliewer
authors.forename: Salaheddin M
authors.initials: SM
authors.lastname: Mahmud
authors.forename: Charles N
authors.initials: CN
authors.lastname: Bernstein
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000401:mortality* / Q000517:prevention & control; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013997:Time Factors