A Case-Control Study of Colorectal Cancer : Evaluation of Risk Factors by Sex and Cancer Site

Abstract

The risk factors for colorectal cancer were investigated in a case-control study involving 177 cases with primary colon cancer, 153 cases with primary rectal cancer and 660 commu nity-based controls in Hokkaido, Japan. The 330 cases underwent abdominal surgery in the 1st Department of Surgery, Sapporo Medical College or associated hospitals during the 4 years from January 1987 to December 1990. Two controls were individually matched with the index cases for sex and age (within 3 years). Using the same questionnaire, the 330 sets of case and two controls were queried regarding demographic factors, smoking and dietary habits, consumption of alcoholic bever- ages, reproductive history, family history of cancer and other similar parameters. For statistical analysis, the student's t-test, Mantel-Haenszel method and logistic regression model were used. The results are summarized as follows : 1. The amount of total absolute alcohol (ethanol), sake drinking and a family history of (any) cancer showed an increased risk of male colon cancer. 2. Consumption of bread (1 time or more a week) and consumption of seafood, other than fish (more than 3 times a week) showed an increased risk of male rectal cancer. 3. Daily intake of black tea was positively associated with the risk of female colon cancer. 4. Consumption of rice (4 cups or more a day), consumption of animal organs (more than 1-2 times a week) and a family history of colorectal cancer were associated with a higher risk of female rectal cancer. 5. The following factors showed a decreased risk of colorectal cancer, namely, consumption of rice (3 times a day regularly) for male colon cancer, beer drinking for male rectal cancer and daily intake of milk and parity (1 or more times versus none) for female colon cancer. There is no clear-cut evidence of a specific mechanism that may explain the positive or negative relationships between these factors and colorectal cancer, nevertheless, as the epidemiological approach to cancer is very significant and may contribute to the primary prevention of cancer, fur ther investigation should be conducted