Primary Care Medical Abstracts

Abstract: Risk of colorectal cancer after a negative colonoscopy in low-to-moderate risk individuals: impact of a 10-year colonoscopy


 

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Murthy, S.K., et al, Endoscopy 49(12):1228, December 2017

BACKGROUND: Repeat colonoscopy is recommended ten years after a negative screening for colorectal cancer (CRC) in low-risk persons, but the real-world benefit of this recommendation is uncertain.

METHODS: These Canadian authors, coordinated at the University of Ottawa, performed a retrospective cohort study to determine the utility of ten-year repeat screening colonoscopy using population-level data from Ontario adults aged 50-74 years with a low to moderate risk of CRC (no relevant gastrointestinal disorders) who had a negative colonoscopy in 1996-2001 and a repeat negative screening within eight to twelve years, excluding those with intervening events (CRC detection, colectomy, or lower endoscopy). The primary outcome was early incident CRC in the group having repeat screening within twelve years compared with an unexposed control group matched by age, sex and year of baseline colonoscopy.

RESULTS: A total of 13,350 matched pairs (median age 68 years; 56% female) were analyzed for CRC incidence over a median follow-up of 4.5 years. The cumulative probability of CRC over three, five and eight years following a negative baseline colonoscopy was 0.16%, 0.30%, and 0.54%, respectively. Among patients having repeat colonoscopy, 46 developed CRC, compared with 52 in unexposed controls, for cumulative probabilities of 0.70% and 0.77%, respectively, and a hazard ratio of 0.91 (95% CI 0.68-1.22) after adjusting for competing risks and comorbidity burden. CRC-related mortality was also similar between groups (8 and 9 patients). Short follow-up was a study limitation.

CONCLUSIONS: Repeat colonoscopy within eight to twelve years of a negative screen was not associated with subsequent CRC incidence, which raises questions about the utility of ten-year repeat screening. 21 references ( smurthy@toh.on.ca – no reprints)

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