Cross-country comparisons of colon and rectal cancer mortality suggest the existence of differences in risk factors in eastern and western Europe.

A comparison of relative mortality rates from colon and rectal cancers in World Health Organization data for various countries in Europe was undertaken to determine whether the two sites demonstrate a direct link. A significant correlation between figures for colon and rectal cancers was found throughout Europe but limited to males and only at the p < 0.05 level. Cluster analysis revealed marked differences between countries of the former west and east European blocks, the latter having much higher values for rectal cancers. Separation of countries on this basis gave rise to significant correlation between the two sites for both sexes (p < 0.05 and p < 0.001, respectively, for western and eastern males; and p < 0.05 and p < 0.001 for females). In order to assess the possible contribution of factors associated with squamous cell cancers (SCCs), data for buccal and cervical cancers, both more prevalent in eastern than in western Europe, were also compared. Whereas a significant correlation was evident between female rectal and cervical cancers overall and in the western countries (p < 0.05) this was not the case for the eastern countries. The results suggest that the observed excess of rectal cancer mortality in eastern European countries may not be simply due to factors contributing to SCCs, but that country level comparisons of individual harmful and beneficial influences, alone and in combination, might allow the underlying reasons to be explained.