Study 1 Overview (Bretthauer et al)
Objective: To evaluate the impact of screening colonoscopy on colon cancer–related death.
Design: Randomized trial conducted in 4 European countries.
Setting and participants: Presumptively healthy men and women between the ages of 55 and 64 years were selected from population registries in Poland, Norway, Sweden, and the Netherlands between 2009 and 2014. Eligible participants had not previously undergone screening. Patients with a diagnosis of colon cancer before trial entry were excluded.
Intervention: Participants were randomly assigned in a 1:2 ratio to undergo colonoscopy screening by invitation or to no invitation and no screening. Participants were randomized using a computer-generated allocation algorithm. Patients were stratified by age, sex, and municipality.
Main outcome measures: The primary endpoint of the study was risk of colorectal cancer and related death after a median follow-up of 10 to 15 years. The main secondary endpoint was death from any cause.
Main results: The study reported follow-up data from 84,585 participants (89.1% of all participants originally included in the trial). The remaining participants were either excluded or data could not be included due to lack of follow-up data from the usual-care group. Men (50.1%) and women (49.9%) were equally represented. The median age at entry was 59 years. The median follow-up was 10 years. Characteristics were otherwise balanced. Good bowel preparation was reported in 91% of all participants. Cecal intubation was achieved in 96.8% of all participants. The percentage of patients who underwent screening was 42% for the group, but screening rates varied by country (33%-60%). Colorectal cancer was diagnosed at screening in 62 participants (0.5% of screening group). Adenomas were detected in 30.7% of participants; 15 patients had polypectomy-related major bleeding. There were no perforations.
The risk of colorectal cancer at 10 years was 0.98% in the invited-to-screen group and 1.2% in the usual-care group (risk ratio, 0.82; 95% CI, 0.7-0.93). The reported number needed to invite to prevent 1 case of colon cancer in a 10-year period was 455. The risk of colorectal cancer–related death at 10 years was 0.28% in the invited-to-screen group and 0.31% in the usual-care group (risk ratio, 0.9; 95% CI, 0.64-1.16). An adjusted per-protocol analysis was performed to account for the estimated effect of screening if all participants assigned to the screening group underwent screening. In this analysis, the risk of colorectal cancer at 10 years was decreased from 1.22% to 0.84% (risk ratio, 0.69; 95% CI, 0.66-0.83).
Conclusion: Based on the results of this European randomized trial, the risk of colorectal cancer at 10 years was lower among those who were invited to undergo screening.