The Journal of the National Cancer Institute published an article saying that colonoscopy for primary screening might be going too far. I agree! The benefits, harms, and costs have not been determined. Checking the stool for ocult blood and flexible sigmoidoscopy have been shown to be of value but there's no data showing that colonoscopy gives additional protection. Virtual colonoscopy is even more questionable as if there are abnormal findings one still has to do a colonoscopy and there's the issue of radiation damage and later cancer risk.
Yet the American College of Gastroenterology and the National Comprehensive Cancer Network continue to recommend colonoscopy as a primary screening tool. Because of the obvious conflict of interest this is not very surprising.
The benefits of colonoscopy is that 1 in 200 people will have a major benefit from the procedure. However the same number will have either a perforation of the colon or major bleed that requires transfusions. In addition colonoscopy misses a lot of right sided cancers even though it is recommended that all polyps are removed, even those that are of no danger.
Colonoscopy Screening Questioned