Abstract

Three hundred and thirty six forensic necropsy specimens of large bowel were examined in order to identify subject related variables that independently predicted the following adenoma characteristics: presence, size (largest), multiplicity and high grade dysplasia. The variables were age, gender, body mass index, race (European origin versus Maori/Polynesian) and presence of hyperplastic (metaplastic) polyp(s). Subjects included 303 New Zealanders of European origin (M = 185, F = 118) yielding 149 adenomas and 251 hyperplastic polyps and 33 Maori/Polynesians (M = 25, F = 8) yielding five adenomas and one hyperplastic polyp. Independent predictors of adenoma presence as determined by regression analysis were age (p = 0.0001), presence of hyperplastic polyps (p = 0.0001) and male gender (p = 0.05). Models were poor at explaining variation in size, multiplicity, and dysplasia. Larger adenomas occurred more frequently in subjects with multiple adenomas (p = 0.03) and multiple adenomas were probably associated with hyperplastic polyps (p = 0.09) and male gender (p = 0.09) in Europeans. High grade dysplasia was more frequent in women (p = 0.05) and possibly in subjects with hyperplastic polyps (p = 0.2). Body mass index and ethnicity did not predict any adenoma characteristics, but hyperplastic polyp prevalence was influenced by European origin (p = 0.04) and to a lesser extent by body mass index (p = 0.08) as well as presence of adenoma (p = 0.0002) and age ( = 0.005). The association of hyperplastic polyp with presence, multiplicity but not size of adenoma and with a high risk group for colorectal cancer (New Zealanders of European origin) suggests that the hyperplastic polyp serves as a marker for a factor which influences neoplastic evolution at the stages of initiation/transformation but not promotion. Fifty nine per cent of individuals with adenoma(s) did not have hyperplastic polyp(s) emphasising that the last would serve only as a marker of populations and not individuals at high risk of bowel cancer. Low intracolonic butyrate may be the factor linking the expression of the two types of polyp.