Benefit of colon cancer screening with colonoscopy lower than anticipated

A one-time screening colonoscopy reduced the risk of incident colorectal cancer (CRC) by 18% compared with no endoscopic screening. Also, at 10 years, no significantly reduced mortality was detected with or without colonoscopy screening in the NordICC trial.

Screening by colonoscopy is common in many European countries and North America [1]. “However, no randomised trials up to today have been available to quantify the benefits of this screening test for CRC and, therefore, we do not really know how effective it is in terms of the important endpoints of incidence and mortality of CRC,” Prof. Michael Bretthauer (Oslo University, Norway) explained the motivation for the randomised-controlled NordICC trial (NCT00883792). NordICC is the first, randomised, population-based trial to investigate the effect size that CRC screening by colonoscopy has on the incidence and mortality of CRC [1,2]. This magnitude of effect is important not only on an individual level for shared decision-making with a patient but also for the planning of official screening programmes.

The study enrolled 95,000 healthy people between 55 and 64 years of age directly from population registries in the partaking countries of Norway, Poland, Sweden, and the Netherlands. Participants were randomised to either receive an invitation for 1 colonoscopy screening or usual care, which meant no screening in the trial countries. Of the invitees, 42% participated in a colonoscopy. The presented analysis of the 10-year results could not include the 9,780 patients from the Netherlands due to Dutch General Data Protection Regulations.

“In terms of screening performance, it went very well: there was good bowel preparation for the vast majority of the patients; caecal intubation rate exceeded 95%,” Prof. Bretthauer commented on the participant’s characteristics. The screening colonoscopies did not lead to any deaths or perforations and all 15 cases of major bleeding could be managed endoscopically.

In the intention-to-treat population, the result for the primary endpoint of CRC incidence after 10 years revealed a cumulative CRC risk of 1.20% in those without screening compared with 0.98% in those in the invited group. This resulted in a risk ratio (RR) of 0.82 (95% CI 0.70–0.93) or a risk reduction of 18% with screening. Prof. Bretthauer also presented the results of an adjusted per-protocol analysis, which he emphasised are not as trustworthy as those from the intention-to-treat population. “But they are still informative, because what you do, or try to do, is to estimate the effect if everybody had accepted the screening,” he explained. The per-protocol assessment showed an incidence of 1.22% on usual care and 0.84% with colonoscopy screening, leading to a risk reduction of 31% (RR 0.69; 95% CI 0.55–0.83).

As for the secondary endpoint of CRC mortality, the difference between both intention-to-treat groups was low: 0.31% (usual care) versus 0.28% (invited group) with a non-significant risk reduction of 10% (RR 0.90; 95% CI 0.64–1.16). In his summary, Prof. Bretthauer further added that with regard to all-cause mortality, there was no difference between the 2 groups.

1. Bretthauer M, et al. Long-term colorectal cancer incidence and mortality after screening colonoscopy: the NordICC randomised trial. LB08, UEG Week 2022, 8–11 October, Vienna, Austria.
2. Bretthauer M, et al. N Engl J Med. 9 Oct 2022. Doi: 10.1056/NEJMoa2208375.

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Posted on 2 December, 202228 March, 2024