Sigmoidoscopy screening offers 15-year benefit in CRC incidence, mortality

Sigmoidoscopy screening provides a significant and sustained effect on colorectal cancer (CRC) incidence and mortality for 15 years, according to a pooled analysis of randomized trials.

Four large-scale randomized trials of sigmoidoscopy screening in Norway, Italy, the UK, and the US were included in this pooled analysis. The trials included men and women aged 55‒64 years at enrolment.

The authors estimated the cumulative incidence rate ratio (IRR) and mortality rate ratio (MRR), as well as rate differences after 15 years of follow-up comparing screening and usual care in intention-to-treat analyses. They stratified analyses by sex, age at screening, and cancer site.

A total of 274,952 individuals (50.7 percent women) were included in the analyses, of which 137,493 were in the screening group and 137,459 in the usual care group. Screening attendance was 58 percent to 84 percent.

The rate difference for CRC incidence after 15 years was 0.51 cases per 100 persons (95 percent confidence interval [CI], 0.40‒0.63), while the IRR was 0.79 (95 percent CI, 0.75‒0.83). The rate difference for CRC mortality was 0.13 deaths per 100 persons (95 percent CI, 0.07‒0.19), and the MRR was 0.80 (95 percent CI, 0.72‒0.88).

Women, compared with men, derived less benefit from screening for CRC incidence (women: IRR, 0.84, 95 percent CI, 0.77‒0.91; men: IRR, 0.75, 95 percent CI, 0.70‒0.81; p=0.032 for difference) and mortality (women: MRR, 0.91, 95 percent CI, 0.77‒1.17; men: MRR, 0.73, 95 percent CI, 0.64‒0.83; p=0.025 for difference).

No statistically significant difference in screening effect was observed between individuals aged 55‒59 years and those aged 60‒64 years.