Randomized trial of effects of once-only flexible sigmoidoscopy screening on colorectal cancer incidence and mortality: 21-year follow-up

The UK Flexible Sigmoidoscopy Screening Trial randomized men and women aged 55-64 years who indicated that they would attend flexible sigmoidoscopy screening (if invited) to control (no further contact; n=113,195) or intervention (once-only flexible sigmoidoscopy; n= 57,237). Of people in the intervention group, 71% attended screening. 21-year follow-up results have now been published. Cumulative CRC incidence was 3.18% in the intervention group versus 4.16% in the control group (HR 0.76; 95% CI 0.72-0.81); cumulative CRC mortality was 0.97% versus 1.33% (0.75; 0.67-0.83); effects of screening were particularly evident in the distal colorectum (0.59; 0.54-0.64) and not in the proximal colon (0.98; 0.91-1.07). The HR for CRC incidence with screening was lower in men (HR 0.70; 95% CI 0.65-0.76) than women (0.86; 0.79-0.93; p for interaction = 0.0007). Age had no impact on the effect of the screening. The authors conclude that once-only flexible sigmoidoscopy screening reduces CRC incidence and mortality for at least two decades.