Annals of Internal MedicineTwenty-Three–Year Benefits of Sigmoidoscopy Screening for Colorectal Cancer: A Randomized Trial

NORCCAP investigators randomized 98,654 Norwegian adults aged 50 to 64 to once-only sigmoidoscopy screening (with or without fecal immunochemical testing) versus no screening. After 23 years, mortality benefits persisted in men but were not significant in women.

Clinical Considerations

• In men, 23-year CRC incidence was 4.3% with screening versus 6.0% without (risk difference −1.7 percentage points)
• In men, 23-year CRC death was 1.4% with screening versus 2.2% without (risk difference −0.8 percentage points)
• In women, the incidence risk difference was −0.5 percentage points and the mortality difference was not statistically significant
• Screening effect was strongest for rectosigmoid cancer, consistent with the anatomic reach of sigmoidoscopy
• Adding a single fecal immunochemical test to sigmoidoscopy did not change screening benefits
• Findings raise sex-specific questions about screening modality selection that warrant guideline discussion

Practice Applications

• Recognize sigmoidoscopy as a durable CRC screening option with 23-year evidence of sustained benefit in men
• Integrate sex-specific evidence into shared decision-making conversations about screening modality selection
• Consider why distal-only screening may underperform in women, including right-sided cancer distribution patterns
• Monitor forthcoming guideline updates that may address sex-specific screening recommendations
• Avoid extrapolating sigmoidoscopy mortality findings to assume equivalent colonoscopy performance across sexes