An analysis of the age distribution of colon cancer in adenomatosis coli.

For the purpose of elucidating the genetic and environmental interaction in human carcinogenesis, the age distribution of colon cancer in adenomatosis coli (AC) patients in Japan and England were investigated and compated. According to the multiple mutation theory of carcinogenesis, the rate of tumor production is presented by a natural logarithm of the reciprocal of the survival fraction (the proportion on diagnosed colon cancer by age t either among AC patients or total colon cancer cases), and thus is given by a power function of t. The number of hits necessary for colon cancer development in AC patients was estimated to be 4.2 or 4.4 for males and 3.4 or 3.3 for females in Japanese cases, whereas it was 4.7 or 3.9 and 3.6 or 3.2, respectively, in English cases. The estimates are compatible between countries. On the other hand, from the age specific prevalence curve, number of hits in general population was estimated to be 5.0 for both sexes in Japan, which is approximately one hit less than the values for English general population, at least in males. The present results, when taking into account the geographic and/or chronologic variations in colon cancer frequency, suggest that the etiology of colon cancer in younger patients is primarily determined by a genetic predisposition whilst environmental factors are much more influential for the development of colon cancer in older patients.