Colonoscopy and colorectal cancer prevention: some evidence at last ▸

▴ Singh H, Turner D, Xue L, et al. Risk of developing colorectal cancer following a negative colonoscopy examination. Evidence for a 10-year interval between colonoscopies. JAMA2006;295:2366–73.OpenUrlCrossRefPubMedWeb of Science

Colonoscopy is advocated as a screening test to prevent colorectal cancer (CRC) in those over 50 years old. Guidelines suggest a screening interval of 10 years if colonoscopy is normal but the evidence for this recommendation is weak. Singh et al have addressed this issue in a retrospective database study. They identified 35 975 patients that had a colonoscopy without polypectomy or biopsy from the Manitoba Health physicians’ billings claims database from 1 April 1989 to 31 December 2003. The standardised incidence ratio (SIR) for CRC in this cohort was 0.66 (95% confidence interval (CI) 0.56–0.78) one year after the examination and 0.28 (95% CI 0.09–0.65) at 10 years compared with the CRC incidence from the provincial population. These data apply mainly to patients attending for symptoms rather than screening of average risk subjects over the age of 50 years. Furthermore, as with all observational studies, these results could be due to confounding or bias. The magnitude of the reduction in risk of CRC after a normal colonoscopy is therefore uncertain although it is unlikely that this impressive reduction in SIR is all due to confounding factors. This study provides …