New research casts doubt on the effectiveness of screening colonoscopy for preventing colorectal cancer (CRC) and CRC-related death.1
The study showed that patients assigned to undergo screening colonoscopy had an 18% reduction in the risk of CRC over a period of 10 years, but these patients had no significant reduction in the risk of CRC-related death, compared with patients not assigned to screening.
These results, from the NordICC trial, were published in The New England Journal of Medicine.
The randomized trial (ClinicalTrials.gov Identifier: NCT00883792), included 84,585 participants, aged 55 to 64 years, drawn from registries in Poland, Norway, Sweden, and the Netherlands. Participants were randomly assigned to receive an invitation to undergo screening colonoscopy (n=28,220) or to receive usual care (n=56,365).
Of the participants invited to undergo screening, 42.0% (n=11,843) actually did. With a median follow-up of 10 years, 259 cases of CRC were diagnosed in the group invited to screen, and 622 were diagnosed in the usual-care group.
The incidence of CRC at 10 years was 0.98% for the group invited to screen and 1.20% in the usual-care group. This corresponds to an 18% reduction in risk for patients invited to screen (risk ratio [RR], 0.82; 95% CI, 0.70-0.93).
In order to prevent 1 case of CRC within 10 years, 455 people would need to be invited to screen, the researchers calculated.
The incidence of CRC-related death at 10 years was 0.28% in the invited group and 0.31% in the usual-care group, a nonsignificant difference (RR, 0.90; 95% CI, 0.64-1.16). The risk of death from any cause was similar between the 2 groups as well.
The researchers also performed an adjusted analysis to estimate the effect of screening if all the participants assigned to undergo screening actually did.
In this analysis, the incidence of CRC at 10 years was 1.22% in the usual-care group and 0.84% in the screening group (RR, 0.69; 95% CI, 0.55-0.83). The incidence of CRC-related death was 0.30% and 0.15%, respectively (RR, 0.50; 95% CI, 0.27-0.77).
“This relatively small reduction in the risk of colorectal cancer and the nonsignificant reduction in the risk of death are both surprising and disappointing,” wrote authors of a related editorial.2
“There are several potential explanations for these discouraging results,” they continued. “For example, screening can be effective only if it is performed; only 42% of the participants in the NordICC trial who were invited to undergo screening underwent colonoscopy.”
Other potential explanations are that the benefits of screening colonoscopy take time to be realized, and colonoscopy is highly operator-dependent, the editorialists wrote.
The American Gastroenterological Association (AGA) echoed these sentiments in a statement about the NordICC trial results.3 The AGA said colonoscopy screening is effective if it is completed, the quality of screening matters, and the benefits of colonoscopy take time.
“Detection and removal of polyps prevent future cancers,” the statement said. “If we assume that the ‘usual care’ patients had a similar rate of pre-cancerous polyps that are not removed, it will take time before they develop CRC. Hence, differences between the two groups may increase with longer follow-up, which is planned.”
The AGA also noted that the results of the NordICC trial are not necessarily applicable to CRC screening in the United States.
Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.
1. Bretthauer M, Loberg M, Wieszczy P, et al. Effect of colonoscopy screening on risks of colorectal cancer and related death. N Engl J Med. Published online October 9, 2022. doi:10.1056/NEJMoa2208375
2. Dominitz JA, Robertson DJ. Understanding the results of a randomized trial of screening colonoscopy. N Engl J Med. Published online October 9, 2022. doi:10.1056/NEJMe2211595
3. American Gastroenterological Association. Nordic CRC study: 3 things to know + talking points for patients. Published online October 11, 2022. Accessed October 14, 2022.