Age distribution of right- and left-sided colorectal cancers.

: The age distributions in different anatomic areas of the colorectum were compared in 410 patients. The average age for patients with right-sided cancers (71.3 yr) was significantly higher than that for patients with left-sided cancers (67.5 yr). In addition, there was a significantly higher percentage of patients over the age of 70 (mean age of the whole group) in the right colon group as compared with the left colon group. It was concluded that the older age distribution of right-sided cancers might be explained by the delayed effect of an environmental carcinogen in a population with a longer life expectancy.