Flexible sigmoidoscopy screening, both with and without faecal occult blood testing, reduces colorectal cancer deaths, suggests a recent study.
The randomised clinical trial comprised a total of 98,792 participants aged 50-64 years. Individuals in Norway were randomly sampled and invited for screening, comprising a total of 20,572 people in the screening group. The remaining 78,220 sampled individuals, who were not contacted, formed the control group and were not offered screening. The screening group were further randomised – 10,283 participants received a flexible sigmoidoscopy, with the other 10,289 receiving flexible sigmoidoscopy and faecal occult blood testing (FOBT).
Researchers analysed incidence of, and mortality from, colorectal cancer, over a median follow up of 11 years. Any participants with positive test screening results were offered a colonoscopy.
Screening significantly reduced the risk of death from colorectal cancer by 27%, compared with non-screened participants. This increased to 42% when analysis was restricted to males only, compared to the control group. Flexible sigmoidoscopy and FOBT were more effective at reducing mortality from colorectal cancer, when compared to controls, than flexible sigmoidoscopy alone. The former significantly reduced the risk of death by 38%, while flexible sigmoidoscopy alone did not significantly reduce this risk. The number needed to invite for screening to prevent one colorectal cancer death over 10 years was 1547.
Colorectal cancer incidence was reduced by 20% in the screening group, compared to controls. When the participants were grouped according to age, incidence was reduced by 32% in the 50-54-year age group, and by 17% in the 55-64-year age group. There was no difference between the flexible sigmoidoscopy only versus the flexible sigmoidoscopy and FOBT screening groups.
The researchers noted that ‘compared with no screening, once-only flexible sigmoidoscopy screening or flexible sigmoidoscopy with FOBT reduced colorectal cancer incidence and mortality’. Theysaid their results also show, for the first time in a trial of comparable follow-up, that ‘participants aged 50 to 54 years benefit as much from flexible sigmoidoscopy screening as those older than 55 years, with respect to colorectal cancer incidence.’
This form of screening is currently being tested in the NHS bowel cancer screening pilot.