RISK OF INVASIVE-CARCINOMA IN COLORECTAL ADENOMAS ASSESSED BY SIZE AND SITE

Background: The risk of invasive carcinoma developing in colorectal ad enomas is influenced by a number of characteristics of both patients a nd adenomas, and the composition of the sample analysed. Patients and methods: Between 1978 and 1993 more than 20 000 polyps were prospectiv ely documented at the Erlangen Registry of Colorectal Polyps, and anal ysed statistically by logistic regression. Results: The size of the ad enomas proved to be the most important factor for adenomas equal to or larger than 15 mm as compared with smaller lesions. In 5137 diminutiv e adenomas (less than or equal to 5 mm) invasive carcinoma was never f ound. Adenomas in the right-sided colon had a lower risk than those in the left colon or rectum, but with increasing adenoma size, the malig nancy rate showed a right-sided shift. In adenomas of up to 36 mm in d iameter, invasive carcinoma was found more often when they were locate d in the rectum or left colon while adenomas larger than 36 mm were mo re likely to harbour invasive carcinoma when located in the right or l eft colon rather than in the rectum. Conclusions: A multivariate analy sis of 11380 adenomas detected at the first total colonoscopy showed t hat the factors size and site, both of which can be assessed by endosc opic inspection alone, were found to enable a statistically and clinic ally adequate assessment of the malignancy risk.