Randomized controlled trial: Flexible sigmoidoscopy as an adjunct to faecal occult blood testing in population screening

Objectives: Flexible sigmoidoscopy screening at around age 60 can reduce colorectal cancer incidence. Insufficient evidence exists on flexible sigmoidoscopy at age 60 in a population being offered biennial faecal occult blood test screening from age 50. This randomized controlled trial assessed if flexible sigmoidoscopy would be an effective adjunct to faecal occult blood test. Methods: In the Scottish Bowel Screening Programme between June 2014 and December 2015, 51,769 individuals were randomized to be offered flexible sigmoidoscopy instead of faecal occult blood test at age 60 or to continue faecal occult blood test. Those not accepting flexible sigmoidoscopy and those with normal flexible sigmoidoscopy were offered faecal occult blood test. All with flexible sigmoidoscopy-detected neoplasia or a positive faecal occult blood test result were offered colonoscopy. Results: Overall flexible sigmoidoscopy uptake was 17.8%, higher in men than women, and decreased with increasing deprivation (25.7% in the least to 9.2% in the most deprived quintile). In those who underwent flexible sigmoidoscopy, detection rate for colorectal cancer was 0.13%, for adenoma 7.27%, and for total neoplasia 7.40%. In those who underwent colonoscopy after a positive flexible sigmoidoscopy, detection rate for colorectal cancer was 0.28%, adenoma 8.66%, and total neoplasia 8.83%. On an intention to screen basis, there was no difference in colorectal cancer detection rate between the study and control groups. Adenoma and total neoplasia detection rate were significantly higher in the study group, with odds ratios of 5.95 (95%CI: 4.69–7.56) and 5.10 (95%CI: 4.09–6.35), respectively. Conclusions: In a single screening round at age 60, there was low uptake and neoplasia detection rate. Flexible sigmoidoscopy detected significantly more neoplasia than faecal occult blood test alone.