13-Year colorectal cancer risk after lower-quality, higher-quality and no screening colonoscopy: a cohort study

A lower-quality colonoscopy has been shown to be less effective in reducing colorectal cancer (CRC) incidence than a higher-quality colonoscopy, but the comparison with no-screening colonoscopy (noSC) is lacking. We aimed to compare the 13-year risk of developing CRC between persons with I) a higher-quality screening colonoscopy (higherQualSC), II) a lower-quality screening colonoscopy (lowerQualSC), and III) without a screening colonoscopy.

A health-care database (∼20% of the German population) was used to emulate a target trial with three arms: higherQualSC vs lowerQualSC vs noSC at baseline. The quality of screening colonoscopy was categorized based on the polyp detection rate of the examining physician (cut-off: 21.8%). We included persons aged 55-69 years at average CRC risk and CRC screening naïve at baseline. We estimated adjusted cumulative CRC incidence over 13 years of follow-up.

The higherQualSC arm comprised 142,960 persons, the lowerQualSC arm 62,338 persons, and the noSC arm 124,040 persons. The adjusted 13-year CRC risk was 1.77% in the higherQualSC arm, 2.09% in the lowerQualSC arm, and 2.74% in the noSC arm. Compared to the noSC arm, the adjusted relative risk was 0.76 (95% CI: 0.70-0.84) in the lowerQualSC arm and 0.65 (95% CI: 0.60-0.69) in the higherQualSC arm.

Our study shows that a lowerQualSC is also effective in reducing CRC incidence compared to noSC. However, the effect is about one-third less than that of a higherQualSC.