Effect of Invitation to Colonoscopy Screening on Risk of Colorectal Cancer and Risk of Mortality: The NordICC Trial

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In a pragmatic trial reported in The New England Journal of Medicine, Bretthauer et al, on behalf of the Nordic-European Initiative on Colorectal Cancer (NordICC) Study Group, found a reduced risk of colorectal cancer diagnosis but no significant reduction in disease-specific mortality among patients invited to a single colonoscopy screening (of whom 42% underwent screening) vs those not invited to screening.

Study Details

The trial involved presumptively healthy men and women aged 55 to 64 years from population registries in Poland, Norway, and Sweden between 2009 and 2014. Participants were randomly assigned 1:2 to receive an invitation to undergo a single screening colonoscopy (invited group) or to receive no invitation or screening (usual-care group). After random assignment and prior to start of the intervention, 175 participants assigned to the invited group and 419 assigned to the usual-care group were excluded because they had died or had received a diagnosis of colorectal cancer at random assignment but had not yet been identified as such in the registries. Overall, follow-up data were available for 84,585 participants, including 28,220 in the invited group, of whom 11,843 (42.0%) underwent screening, and 56,365 in the usual-care group.

Primary endpoints were the risks of colorectal cancer and related death in intent-to-screen analysis; the secondary endpoint was death from any cause.

Key Findings

Median follow-up was 10.0 years in both groups (interquartile range = 9.9–10.0 years).

During follow-up, colorectal cancer was diagnosed in 259 patients in the invited group vs 622 in the usual-care group. On intention-to-screen analyses, the risk of colorectal cancer at 10 years was 0.98% in the invited group vs 1.20% in the usual-care group (risk ratio [RR] = 0.82, 95% confidence interval [CI] = 0.70–0.93). The number needed to invite to screening to prevent one case of colorectal cancer within 10 years was 455 (95% CI = 270–1,429).

A total of 15 participants undergoing study screening had major bleeding after polyp removal. No perforations were observed, and no screening-related deaths occurred within 30 days after colonoscopy.

Risk of death from colorectal cancer was 0.28% in the invited group vs 0.31% in the usual-care group (RR = 0.90, 95% CI = 0.64–1.16). Risk of death from any cause was 11.03% in the invited group vs 11.04% in the usual-care group (RR = 0.99, 95% CI = 0.96–1.04).

The investigators concluded, “In this randomized trial, the risk of colorectal cancer at 10 years was lower among participants who were invited to undergo screening colonoscopy than among those who were assigned to no screening.”

Michael Bretthauer, MD, PhD, of the Clinical Effectiveness Research Group, University of Oslo, Oslo University Hospital, is the corresponding author for The New England Journal of Medicine article.

Disclosure: The study was funded by the Research Council of Norway and others. For full disclosures of the study authors, visit

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