Analysis of segregation and variance of predisposition to adenomas and colorectal cancer

Segregation analysis of inheritance of adenomas, colorectal cancer (CRC), and multiple primary malignant tumors (MPMT) revealed their low penetrance: from 3.2 to 29% for homozygotes and from 2.0 to 14.4% for heterozygotes. This cast a doubt on the monogenic type of their inheritance, although it formally corresponded to the quasi-dominant type, i.e., only a fraction of the heterozygotes was expressed. Therefore, the multifactorial model of inheritance was tested, which seemed more adequate, because genetic heterogeneity of adenomas, CRC, and MPMT was suggested from the data on genetic correlations between various clinical forms. Predisposition to various clinical forms of adenomas, CRC, and MPMT was shown to be specific, i.e., the ratio between genetic and environmental predisposition-determining factors reflected pathogenetic differences between these diseases. However, analysis of variance which revealed genetic (pathogenetic) distinctions between adenomas, CRC, and MPMT is insufficient to confirm complete nosologic identity of each of these clinical forms.