Colonoscopy must be better than sigmoidoscopy for detecting asymptomatic cancer

A study reported in the New England Journal of Medicine by Dr David Lieberman and colleagues for the Veterans Affairs Study Group in the USA has found that colonoscopy must be more effective than sigmoidoscopy in detecting advanced colonic neoplasms in asymptomatic men.

3121 asymptomatic patients underwent complete examination of the colon. Colonoscopy revealed one or more neoplastic lesions in 37.5% of the patients.

3121 asymptomatic patients. 1% cancer, 2% adenoma with dysplasia, 8% adenoma > 1cm or villous adenoma.

7.9% of those studied had an adenoma of at least 10mm in diameter or a villous adenoma. 1.6% had an adenoma with high-grade dysplasia. Invasive cancer was found in 1% of the sample.

1765 patients had no polyps in the portion of the colon distal to the splenic flexure. Of these patients 2.7% were found to have advanced proximal neoplasms, implying that sigmoidoscopy alone would not have detected the neoplasms in a portion of the sample.

Of 1765 (56%) with normal distal bowel, 3% had proximal pathology.

The researchers feel that that the findings of the study can only be applied to male patients, given that the sample in the study was 96.8% male.

However, Dr Lieberman's team concludes that it must be more effective to use colonoscopy to screen asymptomatic men for colorectal cancer, rather than sigmioidoscopy alone.

"Many advanced colonic neoplasms would not be detected with sigmoidoscopy." Dr David Lieberman