Changing concepts in cancer prevention: limitations and implications for future research in environmental carcinogenesis.

While the cause and nature of certain human cancers are known, definitive preventative guidelines still cannot be offered for many types of tumors. This is partly due to the inherent biostatistical and epidemiological limitations involved in the identification and interpretation of complex carcinogenic risk factors and potential low-risk hazards. Two divergent control strategies have emerged: (a) regulatory programs designed to control or eliminate minute quantities of pollutants in the ambient environment, based on fairly rigid quantitative risk assessment; (b) a biological research effort to understand the fundamental biological mechanisms with the objective of eventually manipulating or intervening in carcinogenesis through chemoprevention or therapy. Apart from more intensified effort on certain already recognized causal factors, current research indicates that the eliminatory approach will have little impact on the cancer burden and that the mechanistic approach, although difficult and slow, represents the most logical alternative. This will require long-term major investments in fundamental research and manpower. This biological approach, however, is largely ignored by the public and legislative bodies concerned with cancer control strategies, partly due to lack of formal input to appropriate national bodies by experts in chemical carcinogenesis. Informed scientists have an important role in ensuring that the public and legislative bodies are aware of current scientific views on carcinogenesis and the need to establish priorities in research.