THE STUDY ON RISK FACTORS ASSOCIATED WITH BREAST CANCER AMONG WOMEN IN TIANJIN, CHINA AND ADELAIDE, AUSTRALIA

To explore the possible explanation of the marked difference in the incidence of breast cancer between Chinese and Australian women, the authors have compared and analysed the results of two case-control studies completed recently in Tianjin, China and Adelaide, Australia. Of 10 known risk factors for breast cancer 9 were significantly higher in level in Adelaide women than in Tianjin women, i.e., women in Adelaide were much taller, heavier, more obese, earlier at menarche, later at first full-term pregnancy, more nulliparous, less parity, more in history of breast cancer in first degree relatives, more educated. From the 7 risk factors analysed by use of logistic regression model 5 factors, i.e., earlier age at menarche, later age at first full-term pregnancy, less parity, history of benign disease, and history of breast cancer in first degree relatives, were associated significantly with the increased risk for breast cancer in the Tianjin study, but not in Adelaide study. These factors being not associated with breast cancer in Adelaide women were unexpected. The explanation of the indefinite findings in Adelaide study was due to the fact that the level of the risk factor is universally high, relatively uniform and lack of categories. The difference in the risk factor distribution between cases and controle would not be seen in case-control studies, and significance of the risk factor therefore may not be found. According to data on diet survey in these two cities, the calories from fat was significantly higher in Adelaide women than in Tianjin women. The marked difference in incidence in women in the two cities resulted from the summing-up effect of a number of factors. The important role of fat intake in geographical incidence difference and in the development of breast cancer was also discussed.