A single screening procedure could reduce the risk of colorectal cancer for decades, Norwegian trial findings indicate.
Once-only flexible sigmoidoscopy to screen for CRC and remove precancerous lesions provided sustained benefits, according to 23-year follow up of the Norwegian Colorectal Cancer Prevention (NORCCAP) trial.
Men experienced a far greater reduction in CRC incidence than women with the procedure, which involves using a thin, flexible tube to view the lower part of the large bowel.
Their risk of death relating to the cancer also decreased by a third, with no significant survival benefits for women.
“Our findings suggest that a single flexible sigmoidoscopy can have a long-lasting effect on CRC incidence and death,” reported Edoardo Botteri, PhD, from the Norwegian Institute of Public Health in Oslo in the Annals of Internal Medicine.
CRC is the third most common cancer worldwide and, while several screening tests are available, there is not enough evidence to recommend one over another.
As a result, many countries use fecal immunochemical testing (FIT) for CRC screening, whereas others use endoscopic screening with colonoscopy or sigmoidoscopy.
To investigate the potential benefits of sigmoidoscopy further, the team randomly assigned Norwegians aged between 50 and 64 year and living in the city of Oslo or Telemark county to either a once-only sigmoidoscopy examination or usual care without screening in a 1:3 ratio.
Participants invited for flexible sigmoidoscopy were further randomly assigned to either bring or not to bring three successive stool samples for fecal blood testing on attending their sigmoidoscopy procedure.
Those with positive screening results—involving any polyp at least 10 cm, any adenoma, CRC, or positive FIT result—were referred for colonoscopy within six weeks. Adherence to colonoscopy after a positive sigmoidoscopy result was 96%.
Overall, 100,210 persons were randomly assigned to a group, and 98,654 were included in intention-to-screen analyses.
This included 20,552 individuals in the screening group and 78,102 in the no-screening group. Participation with screening was 61.4% in men and 64.7% in women.
In men, the 23-year cumulative risk for CRC was 4.3% with screening and 6.0% without, while in women the corresponding risks were 4.2% and 4.7%.
In men, the 23-year cumulative risk for CRC death was 1.4% in the screening group and 2.2% in the no-screening group, while for women this was 1.3% and 1.4%, respectively.
The effect was strongest for rectosigmoid cancer. Adding fecal blood testing to sigmoidoscopy did not change the benefits of screening.
“Our findings indicate that among men screening was associated with an approximately 28% reduction in CRC incidence and a 37% reduction in CRC death over long-term follow-up, corresponding to absolute risk reductions of 1.7 and 0.8 percentage points, respectively,” the researchers reported.
“In women, screening was associated with a more modest relative risk reduction in CRC incidence (11%; absolute reduction, 0.5 percentage points), with no corresponding reduction in CRC death.”
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