Background: The effectiveness of colonoscopy in preventing colorectal cancer (CRC) within opportunistic screening programs has not been clearly established. The aim of this study was to analyze the effectiveness of colonoscopy within an opportunistic screening program using nested case-control study.
Methods: Subjects who received a diagnosis of CRC (CG) between the ages of 50 and 90 years were included and matched by age and gender in a 1:5 ratio with patients without CRC diagnosis (COG) during the period 2015 to 2023. Using conditional regression analyses, we tested the association between screening colonoscopy and CRC. Subgroup analyses were then performed for CRC location, endoscopist specialty, and colonoscopy quality.
Results: Of the 134 patients in CG, 19 (14.18%) had a colonoscopy in the preceding 5 years compared with 258 out of 670 (38.51%) in COG (AOR, 0.24; 95% CI: 0.14-0.41). Any colonoscopy was strongly associated with decreased odds for left-sided CRC (AOR, 0.09; 95% CI: 0.04-0.24) but not for right-sided CRC (AOR, 0.58; 95% CI: 0.29-1.17). Only complete colonoscopy (AOR, 0.41; 95% CI: 0.19-0.89) and colonoscopy with satisfactory bowel preparation (AOR, 0.38; 95% CI: 0.15-0.98) were associated with decreased odds for right-sided CRC. No significant differences in colonoscopy outcomes were found when stratifying by endoscopist specialty.
Conclusions: In the setting of an opportunistic screening program, exposure to any colonoscopy significantly reduced left-sided CRC incidence; however, only high-quality colonoscopy was associated with a lower incidence of right-sided CRC. Therefore, every possible effort should be made to optimize the quality and cost-effectiveness of colonoscopy within an opportunistic screening program.
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