[Epidemiologic cancer research--new aspects for health education and early detection?].

Effective prevention has in the first place to be based on the knowledge of causal factors. In preventive oncology difficulties arise from the fact that our knowledge of causal mechanisms is--with some exceptions--not sufficient to provide clear guidelines for preventive action. Furthermore, it seems beyond doubt that development of cancer is a multifactorial process in which individual disposition, age and exposure to carcinogens participate. Only exposure can be modified by preventive measures. Epidemiological analysis of available data suggests that the effect of environmental carcinogens such as air pollution, contamination of food or occupational hazards on the general population is usually overestimated, although their effect cannot be ignored altogether. On the other hand, the real impact of tobacco products on carcinogenesis seems not yet to be fully realized. Not enough details are known about the probably major importance of dietary habits. In secondary prevention screening programs for the general population are only to be recommended at present for early detection of carcinoma of the cervix uteri. On the other hand, selective case finding in general practice, on the basis of knowledge of risk factors which are at least partially known, could be substantially improved.