Risk of Incident Colorectal Cancer and Death After Colonoscopy: A Population-based Study in Utah

Background & Aims: Colonoscopy is widely recommended for colorectal (CRC) screening in the United States, but evidence of effectiveness is limited. We examined whether exposure to colonoscopy decreases the odds of incident CRC and death from CRC in Utah. Methods: We performed a case-control study of Utah residents, 54 to 90 years old, who received a CRC diagnosis from 2000 through 2010 (cases). Age- and sex-matched controls with no history of CRC (controls) were selected for each case. We determined receipt of colonoscopy 6 months to 10 years before the reference date for each case and control through administrative claims data. Colonoscopy exposure was compared by using conditional logistic regression. Results: We identified 5128 cases and 20,512 controls; 741 cases (14%) and 5715 controls (28%) received a colonoscopy. Exposure to colonoscopy reduced the odds for a diagnosis of CRC; the odds ratios (ORs) were 0.41 for any CRC (95% confidence interval [CI], 0.38-0.44), 0.58 for proximal colon cancer (95% CI, 0.51-0.65), and 0.29 for distal colon or rectal cancer (95% CI, 0.25-0.33). This finding was consistent among sexes, age groups, and cancer stages. Similarly, in a subgroup analysis, colonoscopy was associated with decreased odds of death from CRC (OR, 0.33; 95% CI, 0.28-0.39) in both the proximal colon (OR, 0.43; 95% CI, 0.34-0.55) and distal colon or rectum (OR, 0.23; 95% CI, 0.18-0.30). Conclusions: In the population of Utah, colonoscopy is associated with a large reduction in risk of new-onset CRC and death from CRC. This reduction in risk for CRC was greatest for the distal colon and rectum, with a more modest reduction for proximal colon cancer.