Effectiveness of Colonoscopy Screening vs Sigmoidoscopy Screening in Colorectal Cancer

Area of Science:

• Gastroenterology
• Preventive Medicine
• Oncology

Background:

• Randomized trials confirm sigmoidoscopy screening reduces colorectal cancer (CRC) incidence and mortality.
• Colonoscopy has become the preferred CRC screening method, yet long-term trial data are limited.

Purpose of the Study:

• To estimate the comparative effectiveness of colonoscopy screening versus sigmoidoscopy screening for CRC prevention.
• To quantify the additional screening benefit of colonoscopy beyond sigmoidoscopy.

Main Methods:

• A simulation study pooling data from 358,204 participants in 4 randomized sigmoidoscopy screening trials (1993-2001).
• Estimated colonoscopy effectiveness by assuming similar efficacy in the proximal and distal colon, validated with Norwegian trial data.
• Primary outcomes included CRC incidence and mortality over a 15-year follow-up period.

Main Results:

• Colonoscopy screening was associated with an estimated 30% reduction in CRC incidence and 32% reduction in CRC mortality compared to usual care.
• The additional benefit of colonoscopy over sigmoidoscopy was 6.9% fewer CRC cases and 7.6% fewer CRC deaths per 100,000 person-years.
• The number needed to switch from sigmoidoscopy to colonoscopy to prevent one CRC case was 560, and to prevent one CRC death was 1611.

Conclusions:

• Colonoscopy screening provides an additional preventive effect on CRC incidence and mortality compared to sigmoidoscopy.
• The incremental benefit of colonoscopy over sigmoidoscopy is smaller than the benefit sigmoidoscopy offered over no screening.
• These findings likely represent the upper limit of the additional benefit achievable by switching from sigmoidoscopy to colonoscopy screening.