Trending Clinical Topic: Colonoscopy

Ryan Syrek


October 21, 2022

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From celebrities advocating for colonoscopies by sharing their own to new findings about just how much the procedure affects colorectal cancer (CRC) risk and mortality, various news about the screening method resulted in this week's top trending clinical topic. At United European Gastroenterology (UEG) Week 2022, researchers presented findings from a 10-year follow-up of the large, multicenter, randomized Northern-European Initiative on Colorectal Cancer (NordICC) trial. Results showed that a single screening colonoscopy was beneficial, but perhaps not as much as expected (see Infographic).

The study was designed to be truly population-based and to mimic national CRC screening programs. All persons invited to undergo colonoscopy screening were compared with people who received usual care (ie, no invitation or screening). The interim 10-year CRC risk was found to be 0.98% in the invited group, compared with 1.20% in the usual care group (risk ratio, 0.82; 95% CI, 0.70-0.93). This suggests that 455 individuals would need to be invited to undergo colonoscopy to prevent one case of CRC (95% CI, 270-1429). The risk for death from colorectal cancer was 0.28% in the invited group and 0.31% in the usual care group (risk ratio, 0.90; 95% CI, 0.64-1.16).

Experts have pointed to several concerns about the study, including the fact that only 42% of those invited actually underwent colonoscopy. An editorial that accompanied publication of the study points out that cohort studies have found a 40%-69% decrease in the incidence of CRC and a 29%-88% decrease in mortality risk. However, the authors note "cohort studies probably overestimate the real-world effectiveness of colonoscopy because of the inability to adjust for important factors such as incomplete adherence to testing and the tendency of healthier persons to seek preventive care." The editorialists also suggest that benefits colonoscopy screening take time "because the incidence of CRC is initially increased when pre-symptomatic cancers are identified." They also note that "colonoscopy is highly operator dependent" and that the adenoma detection rate varies and affects cancer risk and related mortality.

A separate recent study found that, for individuals who do not have an adenoma detected on an index colonoscopy, the risk of developing an advanced neoplasia (AN) and CRC is lower among those aged 40-49 years compared with those aged 50-59 years. However, no difference was found between the two age groups in detection rates of nonadvanced adenoma (NAA) or advanced adenoma (AA). The study included 2396 individuals aged 40-49 years and 8978 individuals aged 50-59 years. Screening colonoscopy was performed in 40.2% of the younger group vs 34.8% of the older group; it was prompted by a positive fecal immunochemical test result in 3.3% of the younger group vs 32% of the older group.

The authors found that "when comparing the 40-49 years group to the 50-59 years group, index colonoscopy detected no adenoma in 62.9% versus 40.1% (P < .0001); NAA in 25.4% versus 39.0% (P <.001), and AA in 11.6% versus 21.0% (P < .0001), respectively." When the two age groups were compared for surveillance colonoscopy, no adenoma was detected in 67% of the younger group vs 54.7% of the older group (P < .0001), whereas NAA was detected in 25.4% vs 38.4%, respectively (P < .0001). AA was detected in 3.5% vs 6.95% (P < .0001), respectively. AN was detected on surveillance colonoscopy after index colonoscopy in 2.2% of the younger group and 4.4% in the older group (P = .0003). On surveillance colonoscopy, NAA was found in 4.6% vs 7% (P = .03), respectively. AA was found in 7.9% vs 11.7%, respectively (P = .06).


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