A case-control study on alcohol drinding habit, ALDH2 genotype and colorectal cancer.

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A case-control study was conducted to explore a possible etiological role of alcohol drinking habit in colorectal cancer. Cases were 243 colon and 147 rectum cancer patients who were surgically treated in Chiba Cancer Center Hospital during the period 1989 through 1997. Controls were 1,124 persons including both patients of benign diseases and attendants of a health check program. Information on their life styles such as drinking, smoking and dietary habits was collected by a self-administered questionnaire. For a part of them (210 cases and 303 controls), alcohl tolerance was also checked by a DNA test of ALDH2 genotypes with the PCR method. Japanese population shows inter-individual variation of aldehyde dehydrogenase activity due to a polymorphism of this gene, with alcohol tolerant 1/1 homozygotes, intermediate 1/2 heterozygotes and intolerant 2/2 homozygotes.According to a uni-variate analysis with the chi-square statistical test, the factors such as daily amount of alcohol consumption, frequent intake of meat, and irregular, hastened and excess meal habits were all significantly associated with both colon and rectum cancers, whereas infrequent intake of milk and fish was associated only with rectum cancer. Daily amount of tobacco smoked, intake frequency of fruits and vegetables were not different between cases and controls. These results remained unchanged even after a multi-variate logistic regression analysis was performed. If the ALDH2 genotype was included in the multi-variate analysis, this genotype instead of alcohol consumption showed signficant association with colon cancer, indicating that reduced enzyme activity in the heterozygotes is a risk factor for colon cancer. This is most prominent for sigmoid colon cancer. No such relation was found for rectum cancer. It is concluded that excess alcohl drinking is a risk factor for colorectal cancer and that the heterozygotes of ALDH2 are especially a high-risk group for colon cancer.