Fecal occult blood and flexible sigmoidoscopy screening for colorectal cancer: modeling the impact on colonoscopy requirements and cancer detection rates.

AIM: The aim of this study was to estimate the colonoscopy requirements and the likely impact of fecal occult blood and flexible sigmoidoscopy screening on the detection of colorectal cancer by using previously published data.

METHODS: Fecal occult blood and flexible sigmoidoscopy screening programs were applied to the 2.04 million subjects aged 50-65 years, at a participation rate of 40%. The following strategies were evaluated: Fecal occult blood testing with colonoscopy follow up of all positive tests; flexible sigmoidoscopy with colonoscopy follow up of all adenomatous polyps; and flexible sigmoidoscopy with colonoscopy follow up of all adenomatous polyps > 10 mm in size.

RESULTS: The fecal occult blood program detected 5.6% of all colorectal cancer cases at a rate of 2,914 colonoscopies/percentage of detection of colorectal cancer. The flexible sigmoidoscopy program detected 14% of all colorectal cancer cases at a rate of 8,160 colonoscopies/percentage of detection of colorectal cancer. The flexible sigmoidoscopy program with follow up of adenomatous polyps > 10 mm in size detected 13% of all colorectal cancer cases at a rate of 1,230 colonoscopies/percentage of detection of colorectal cancer.

CONCLUSIONS: Flexible sigmoidoscopy screening followed by colonoscopic follow up of adenomatous polyps > 10 mm in size is the most efficient screening strategy in terms of colonoscopies generated and cases of colorectal cancer detected.