Sigmoidoscopy screening cuts colorectal cancer incidence, mortality

Sigmoidoscopy and guaiac faecal occult blood test (gFOBT) screening confer benefits for colorectal cancer incidence or mortality, according to a network meta-analysis.

Researchers searched multiple online databases for randomized controlled trials that evaluated the impact of annual or biennial gFOBT or faecal immunochemical test (FIT), once-only sigmoidoscopy on the following outcomes: colorectal cancer incidence and mortality, all-cause mortality, harms (bleeding, perforation, screening-related death and other major and minor complications), and burdens (need for further diagnostic workup including colonoscopy, procedure-related pain, psychological impact of a positive test and absence from work).

A total of 12 trials were included in the network meta-analysis: five on gFOBT screening, two on FIT screening, five on sigmoidoscopy screening and two on colonoscopy screening. The overall population comprised 1,325,618 participants aged 45–80 years with follow-up ranging from 0 to 19.5 years for colorectal cancer incidence and from 0 to 30 years for colorectal cancer mortality.

Compared with no-screening, sigmoidoscopy screening produced numerical reductions in colorectal cancer incidence (relative risk [RR], 0.76, 95 percent CI, 0.70–0.83) and mortality (RR, 0.74, 0.69–0.80), whereas gFOBT screening exerted little or no difference in colorectal cancer incidence but marginally decreased colorectal cancer mortality (annual: RR, 0.69, 0.56–0.86; biennial: RR, 0.88, 0.82–0.93). None of the screening test examined reduced colorectal cancer mortality or incidence by >6 per 1,000 screened over 15 years.

Notably, sigmoidoscopy had a stronger effect in men, for both colorectal cancer incidence (women: RR, 0.86, 0.81–0.92; men: RR, 0.75, 0.71–0.79) and mortality (women: RR, 0.85, 0.71–0.96; men: RR, 0.67, 0.61–0.75).

The present data demonstrate that sigmoidoscopy screening slightly reduces colorectal cancer incidence even 15 years after a once-only screening, according to researchers. To date, most guidelines recommend rescreening 5–10 years after initial screening. This may now be safely extended to 15 years.