Twenty-Three–Year Benefits of Sigmoidoscopy Screening for Colorectal Cancer

BACKGROUND: Meta-analyses of randomized trials have shown that sigmoidoscopy screening reduces colorectal cancer (CRC) incidence and death for 15 years. OBJECTIVE: To report the benefits of sigmoidoscopy after 23 years. DESIGN: Randomized controlled trial. (NORCCAP [Norwegian Colorectal Cancer Prevention], ClinicalTrials.gov: NCT00119912). SETTING: Population of Oslo and Telemark County, Norway. PARTICIPANTS: Persons aged 50 to 64 years without CRC at randomization. INTERVENTION: Screening with once-only sigmoidoscopy, with or without 1 fecal immunochemical test, or no screening. MEASUREMENTS: Colorectal cancer incidence and death. RESULTS: A total of 100 210 persons were randomly assigned, and 98 654 were included in intention-to-screen analyses: 20 552 in the screening group and 78 102 in the no-screening group. Participation with screening was 61.4% in men and 64.7% in women. In men, the 23-year cumulative risk for CRC was 4.3% in the screening group and 6.0% in the no-screening group, corresponding to a risk difference of -1.7 percentage points (95% CI, -2.2 to -1.2 percentage points). In women, the corresponding risks were 4.2% and 4.7%, yielding a risk difference of -0.5 percentage points (CI, -1.0 to -0.01 percentage points). In men, the 23-year cumulative risk for CRC death was 1.4% in the screening group and 2.2% in the no-screening group, corresponding to a risk difference of -0.8 percentage points (CI, -1.1 to -0.5 percentage points). In women, the corresponding risks were 1.3% and 1.4%, yielding a risk difference of -0.1 percentage points (CI, -0.3 to 0.1 percentage points). The effect was strongest for rectosigmoid cancer. The addition of fecal blood testing to sigmoidoscopy did not change screening benefits. LIMITATION: Follow-up through national registries. CONCLUSION: Offering sigmoidoscopy screening in Norway reduced CRC incidence more in men than in women and reduced CRC death only in men. PRIMARY FUNDING SOURCE: Norwegian government and Norwegian Cancer Society.