OR WAIT null SECS
NordICC: Single Colonoscopy Cuts Colorectal Cancer Incidence but Not Mortality at 13 Years
Updated results from the NordICC trial build upon previous 10 year findings and shed further light on once-only colonoscopy as a primary screening modality.
New 13-year follow-up data from the NordICC randomized controlled trial confirm that a single screening colonoscopy significantly reduces colorectal cancer (CRC) incidence, though the observed reduction in CRC-specific mortality did not reach statistical significance in intention-to-screen analyses.
The updated results, drawn from more than 84,000 participants across Norway, Poland, and Sweden, were presented at Digestive Disease Week (DDW) 2026 in Chicago, IL, by Michael Bretthauer, MD, PhD, a professor of medicine at the University of Oslo, and extend findings previously reported at 10 years, representing the most mature evidence available from a randomized trial evaluating once-only colonoscopy as a primary screening modality.
13-Year NordICC Data on CRC Incidence
The NordICC trial enrolled 84,583 men and women between the ages of 55 and 64 years at baseline and randomly assigned them in a 1:2 ratio to either an invitation for colonoscopy screening or no screening. All analyses were conducted at 13 years of follow-up and reported both intention-to-screen (ITS) and per-protocol (PP) effect estimates.
CRC incidence at 13 years was 1.46% in the screening group (375 cancers among 28,217 participants) compared with 1.80% in the no-screening group (912 cancers among 56,366 participants), yielding an intention-to-screen risk ratio (RR) of 0.81 (95% CI, 0.71–0.90). In per-protocol analyses accounting for the subset of participants who actually underwent colonoscopy, the incidence reduction was larger, with an RR of 0.55 (95% CI, 0.33–0.81).
The differential effect by tumor location was statistically significant. For distal CRC, the screening group showed a risk of 0.87% versus 1.11% in the no-screening group (RR, 0.79; 95% CI, 0.65–0.89), while for proximal CRC, the difference was: 0.51% versus 0.56% (RR, 0.91; 95% CI, 0.71–1.09; P for interaction <.005.).
Sex-stratified analyses showed an incidence reduction in both men (RR, 0.77; 95% CI, 0.64–0.88) and women (RR, 0.87; 95% CI, 0.70–1.02; P for interaction <.005).
Mortality Findings and Background Rate
CRC mortality at 13 years was 0.41% in the screening group and 0.47% in the no-screening group, producing an intention-to-screen RR of 0.88 (95% CI, 0.68–1.08). The per-protocol RR for mortality was 0.70 (95% CI, 0.26–1.25).
Investigators noted the observed CRC mortality in the no-screening group (0.47%) was substantially lower than the 0.82% projected when the trial was designed. This discrepancy directly affects the trial's statistical power to detect a mortality benefit, since the anticipated event rate underpinned the original sample size calculations. The NordICC trial was designed based on an assumed 50% CRC mortality-reducing efficacy of the intervention, with 50% compliance predicted to yield a 25% mortality reduction among those invited to screening.
Study Design, Population, and Context
The NordICC trial enrolled participants between 2009 and 2014 across multiple Nordic and Central European countries. Participants were identified through population registries and followed via national cancer and cause-of-death registries. Randomization used a 1:2 ratio, with 28,217 assigned to the colonoscopy invitation arm and 56,366 to the control arm.
The per-protocol analyses presented at DDW are particularly important for interpreting true colonoscopy efficacy, since roughly 42% of those invited for colonoscopy in the original 10-year publication actually underwent the procedure.
“In this randomised trial, one colonoscopy significantly reduced CRC incidence but not mortality over 13 years. CRC mortality is lower in both study groups than when the trial was designed,” Bretthauer and colleagues concluded.
References
Kaminski MF, Kalager M, Løberg M, et al. LONG-TERM EFFECTS OF COLONOSCOPY SCREENING ON COLORECTAL CANCER INCIDENCE AND MORTALITY: UPDATE FROM THE NORDICC RANDOMISED TRIAL. Presented at Digestive Disease Week (DDW) 2026; Chicago, IL; May 2–5, 2026.
Bretthauer M, Kaminski MF, Løberg M, et al. Population-based colonoscopy screening for colorectal cancer: a randomized clinical trial. JAMA Intern Med. 2016;176(7):894–902.
Bretthauer M, Løberg M, Wieszczy P, et al. Effect of colonoscopy screening on risks of colorectal cancer and related death. N Engl J Med. 2022;387(17):1547–1556.
van den Berg DMN, Nascimento de Lima P, Knudsen AB, et al. NordICC trial results in line with expected colorectal cancer mortality reduction after colonoscopy: a modeling study. Gastroenterology. 2023;165(4):874–882.
