Twenty-three year follow-up of a randomized trial of sigmoidoscopy screening for colorectal cancer

The randomized Norwegian Colorectal Cancer Prevention (NORCCAP) trial investigated benefits of sigmoidoscopy. Twenty-three year follow-up results from the trial have now been published. A total of 100 210 persons aged 50 to 64 years without colorectal cancer (CRC) living in Oslo and Telemark County were randomized to screening with once-only sigmoidoscopy with or without one FIT (n=20 552 in the intention-to-screen analysis) or no screening (n=78 102). Participation with screening was 61.4% among men and 64.7% among women. Among men, the 23-year cumulative risk for CRC was 4.3% in the screening group and 6.0% in the no-screening group (risk difference -1.7 percentage points; 95% CI -2.2 to -1.2), whereas the 23-year cumulative risk for CRC death was 1.4% versus 2.2% (-0.8%; -1.1 to -0.5). Among women, the 23-year cumulative risk for CRC was 4.2% in the screening group and 4.7% in the no-screening group (risk difference – 0.5% percentage points; 95% CI -1.0 to -0.01), whereas the 23-year cumulative risk for CRC death was 1.3% versus 1.4% (-0.1%; -0.3 to +0.1). The effect was strongest for rectosigmoid cancer. The addition of fecal blood testing did not change screening benefits. The authors conclude that offering sigmoidoscopy screening in Norway reduced CRC incidence more in men than in women, and reduced CRC death only in men.