European trial led by Michael Bretthauer fast-tracked in the The Lancet and presented at Digestive Disease Week in Chicago

About the study  

The NordICC study (Nordic-European Initiative on Colorectal Cancer) includes 95,000 participants from Norway, Sweden, Poland, and the Netherlands, and is one of the largest medical intervention studies ever conducted.  

In NordICC, 95,000 healthy people between the ages of 55 and 64 in Norway, Poland, Sweden, and the Netherlands were assigned either to one cancer screening with a colonoscopy or to no screening.  

Screening was conducted from 2009 to 2014, under the leadership of Michael Bretthauer and colleagues at the Clinical Effect Research Group at the University of Oslo and Oslo University Hospital, Oslo, Norway.  

In October 2022, the NordICC investigators published the 10-year results from the trial in the New England Journal of Medicine. The results were much debated across the World. 

Some found the screening benefits in the trial to be smaller, and experts suggested that ten years of follow-up may have been too short to fully ascertain screening benefits. 

The Lancet paper

Here, the NordICC investigators report the effects of colonoscopy screening after three more years of follow-up in intention-to-screen and per-protocol analyses. 

Due to substantially more CRC cases and deaths, the new report now also provides estimates for men and women, proximal and distal colorectal cancers, and people younger versus older than 60 years.  

The new results after 13-years follow-up

CRC incidence

• CRC incidence was 1·46% in the screening group and 1·80% in the no-screening group in intention-to-screen analyses (risk ratio (RR) 0·81 (95% confidence interval [CI] 0·71 to 0·90) 
• The relative CRC incidence reduction was 45% in per-protocol analyses (RR 0·55; 95%CI 0·33-0·81. 
• Colonoscopy was more effective in the distal colon than in the proximal colon

CRC mortality

• CRC mortality was not reduced with colonoscopy screening
• The observed CRC mortality in the non-screening group (0·47%). was significantly lower than expected at the time of designing the trial (0·82%) 
• CRC mortality was 0·41% in the screening group and 0·47% in the no-screening group (intention-to-screen RR 0·88; 95% CI 0·68 to 1·08; per-protocol RR 0·70 (95%CI 0·26 to 1·25).

What do the results mean?

After 13 years, a single colonoscopy reduces CRC risk from about 1.8% to about 1 to 1.5%.

The risk of CRC death is very low even without screening, and the hope of finding a screening benefit on CRC mortality even with longer follow-up is not substantiated.

The gastrointestinal and screening community should consider what is most important for a screening test like colonoscopy. 

Screening might be justified if it prevents people from getting cancer even without reducing the risk of dying. 

On the population level, screening benefits must be weighed against other expenditures which promote public health. 

Links:

The Lancet article:
Long-term effects of colonoscopy screening on colorectal cancer incidence and mortality: a multicountry, population-based randomised controlled trial
Online May 04 2026

News articles (in Norwegian):

Oslo University Hospital - OUS innsikt:
Ny stor studie: Koloskopi forebygger tarmkreft – men mindre enn forventet (oslo-universitetssykehus.no)

University of Oslo:
Nye funn: Koloskopi reduserer forekomst av tarmkreft, men ikke dødelighet (med.uio.no)

NRK - Norwegian Broadcasting Corporation:
Nye funn: Reduserer risikoen for tarmkreft

Dagens Medisin:
Nye funn: Så stor er effekten av koloskopi for å unngå tarmkreft (dagensmedisin.no)

Clinical Effectiveness Research (ous-research.no)

Michael Bretthauer