Abstract
Background and Study Aims: The risk of invasive carcinoma developing in colorectal adenomas is influenced by
a number of characteristics, relating both to the patients and to the adenomas, and
by the composition of the sample analyzed. The aim of the present study was use a
multivariate analysis to investigate the risk of invasive carcinoma in endoscopically
and surgically removed adenomas.
Patients and Methods: Between 1978 and 1993, more than 20,000 polyps were prospectively documented at the
Erlangen Registry of Colorectal Polyps. A multivariate analysis of 11,188 adenomas
detected at the first total colonoscopy was carried out in order to investigate the
risks associated with size and site - both of which can be assessed by endoscopic
inspection alone - and the extent to which these may be modified by other patient
and adenoma characteristics, with an influence on the risk of invasive carcinoma in
colorectal adenomas.
Results: The size of the adenoma proved to be the most important influencing factor. Invasive
carcinoma was never found in 5027 small adenomas (≤ 5 mm). Adenomas in the right colon
had a lower risk than those in the left colon or rectum. But with increasing adenoma
size, the malignancy rate showed a right-sided shift, with a significant interactive
effect of size and right-sided location. However, the risk determined by the size
and site of the adenoma was significantly modified by a number of patient and adenoma
characteristics, including histological type, presence of multiple adenomas, and patient
age and sex.
Conclusions: The risk of invasive carcinoma in colorectal adenomas can only be adequately described
by a complex model of the interactive effects of patient and adenoma characteristics
on the main factors of size and site.
