VIENNA – the 10-year follow-up of the large, multicenter, randomized Northern-European Initiative on Colorectal Cancer (NordICC) trial shows.
In effect, this means the number needed to invite to undergo screening to prevent one case of colorectal cancer is 455 (95% confidence interval, 270-1,429), the researchers determined.
The results were presented at the United European Gastroenterology Week 2022 meeting and were published simultaneously in The New England Journal of Medicine.
The results of the study, which was designed to be truly population based and to mimic national colorectal cancer screening programs, provide an estimate of the effect of screening colonoscopy in the general population.
The primary outcome was determined on an intention-to-screen basis. All persons who were invited to undergo colonoscopy screening were compared with people who received usual care (that is, received no invitation or screening). At UEG 2022, the researchers presented the interim 10-year colorectal cancer risk, which was found to be 0.98%, compared to 1.20%. This represents a risk reduction of 18% among colonoscopy invitees (risk ratio, 0.82; 95% CI, 0.70-0.93). During the study period, 259 cases of colorectal cancer were diagnosed in the invited group versus622 in the usual-care group.
The risk of death from colorectal cancer was 0.28% in the invited group and 0.31% in the usual-care group (RR, 0.90; 95% CI, 0.64-1.16). The risk of death from any cause was similar in both the invited group and the usual-care group, at 11.03% and 11.04%, respectively (RR, 0.99; 95% CI, 0.96-1.04).
The authors noted that the benefit would have been greater had more people undergone screening; only 42% of those who were invited actually underwent colonoscopy. In an adjusted analysis, had all those who had been invited to undergo screening undergone colonoscopy, the 10-year risk of colorectal cancer would have decreased from 1.22% to 0.84%, and the risk of colorectal cancer–related death would have fallen from 0.30% to 0.15%.
The researchers, led by gastroenterologist Michael Bretthauer, MD, from the department of medicine, gastrointestinal endoscopy, University of Oslo, who presented the data at UEG 2022 on behalf of the NordICC study group, acknowledged that, despite the “observed appreciable reductions in relative risks, the absolute risks of the risk of colorectal cancer and even more so of colorectal cancer–related death were lower than those in previous screening trials and lower than what we anticipated when the trial was planned.”
However, they add that “optimism related to the effects of screening on colorectal cancer–related death may be warranted in light of the 50% decrease observed in adjusted per-protocol analyses.”
With his coauthors, Dr. Bretthauer wrote that even their adjusted findings “probably underestimated the benefit because, as in most other large-scale trials of colorectal cancer screening, we could not adjust for all important confounders in all countries.”
Dr. Bretthauer also noted that results were similar to those achieved through sigmoidoscopy screening. By close comparison, sigmoidoscopy studies show the risk of colorectal cancer is reduced between 33% and 40%, according to per protocol analyses. “These results suggest that colonoscopy screening might not be substantially better in reducing the risk of colorectal cancer than sigmoidoscopy.”
