Twenty-Three-Year Benefits of Sigmoidoscopy Screening for Colorectal Cancer : A Randomized Trial.

BACKGROUND

Meta-analyses of randomized trials have shown that sigmoidoscopy screening reduces colorectal cancer (CRC) incidence and death for 15 years.

OBJECTIVE

To report the benefits of sigmoidoscopy after 23 years.

DESIGN

Randomized controlled trial. (NORCCAP [Norwegian Colorectal Cancer Prevention], ClinicalTrials.gov: NCT00119912).

SETTING

Population of Oslo and Telemark County, Norway.

PARTICIPANTS

Persons aged 50 to 64 years without CRC at randomization.

INTERVENTION: Screening with once-only sigmoidoscopy, with or without 1 fecal immunochemical test, or no screening.

MEASUREMENTS: Colorectal cancer incidence and death.

RESULTS

A total of 100 210 persons were randomly assigned, and 98 654 were included in intention-to-screen analyses: 20 552 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% in the screening group and 6.0% in the no-screening group, corresponding to a risk difference of -1.7 percentage points (95% CI, -2.2 to -1.2 percentage points). In women, the corresponding risks were 4.2% and 4.7%, yielding a risk difference of -0.5 percentage points (CI, -1.0 to -0.01 percentage points). 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, corresponding to a risk difference of -0.8 percentage points (CI, -1.1 to -0.5 percentage points). In women, the corresponding risks were 1.3% and 1.4%, yielding a risk difference of -0.1 percentage points (CI, -0.3 to 0.1 percentage points). The effect was strongest for rectosigmoid cancer. The addition of fecal blood testing to sigmoidoscopy did not change screening benefits.

LIMITATION: Follow-up through national registries.

CONCLUSION

Offering sigmoidoscopy screening in Norway reduced CRC incidence more in men than in women and reduced CRC death only in men.

PRIMARY FUNDING SOURCE: Norwegian government and Norwegian Cancer Society.