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Invitations for screening colonoscopy reduces risk of colorectal cancer

Inviting patients for screening colonoscopy has been found to be associated with a significantly lower 10-year risk of colorectal cancer

Patients who take up an invite for screening colonoscopy have a significantly reduced risk of developing colorectal cancer after 10 years according to the findings of a randomised trial by the NordICC study group.

In 2020, the World Health Organisation estimated that globally, there were 1.93 million cases of colorectal cancer and which resulted in 916,000 deaths. There are a variety of tests available for colorectal cancer screening and to date only the guaiac-based faecal occult blood test and sigmoidoscopy have been shown to reduce the incidence of colorectal cancer and its associated mortality in randomised trials. In addition to sigmoidoscopy, another endoscopic method is screening colonoscopy and which is considered to be the gold standard tool with a high sensitivity and specificity. However, to date, there are no large-scale randomised trials comparing the effectiveness of screening colonoscopy compared to no screening, to determine whether this impacts on the incidence of colorectal cancer.

In the present study, researchers created the Northern-European Initiative on Colorectal Cancer (NordICC) trial, which was a randomised trial investigating the effect of colonoscopy on colorectal cancer incidence and mortality. The trial enrolled individuals aged 55 to 64 who had not undergone previous screening and were randomised 1:2 to either an invitation to undergo screening colonoscopy or no invitation. The primary endpoint of the trial were the risks of colorectal cancer and death from the cancer after a 10 to 15 years, whereas the secondary endpoint was death from any cause.

Screening colonoscopy and cancer outcomes

A total of 84,585 individuals with a median age of 59 years (49.8% female) were enrolled, 28,220 of whom were invited for screening and who were followed-up for a median of 10 years. However, only 11,842 (42%) of participants accepted the invite and underwent screening.

The risk of colorectal cancer at 10 years was 0.98% in the invited group and 1.2% in the usual care (i.e., non-invited group), which was associated with an 18% lower risk of cancer (Risk ratio, RR = 0.82, 95% CI 0.70 – 0.93). However, the risk of colorectal cancer-related death was not significantly different between the groups (RR = 0.90, 95% CI 0.64 – 1.16). In addition, during the follow-up period, there was a similar level of death (11%) from any cause, in both groups.

The above data related to those who responded to the invite for screening but when researchers undertook a per-protocol analysis, i.e., assuming that all invitees underwent screening, the results were even more impressive. The risk of colorectal cancer at 10 years was reduced even further (RR = 0.69, 95% CI 0.55 – 0.83) as was the risk of colorectal cancer death (RR – 0.50, 95% CI 0.27 – 0.77).

The authors concluded that inviting patients for screening colonoscopy reduced the 10-year risk of colorectal cancer compared to those who were not screened.

Bretthauer M et al. Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death N Eng J Med 2022