Causes of cancer and cancer prevention.

Current understanding of the complex processes of cancer causation through a study of the mechanisms of carcinogenesis have documented that there are several major steps each, with distinct quantitative risk assessment factors. The first series of steps, defined by genotoxicity, deal with the assessment of the type of genotoxic carcinogen and its metabolism, leading to a DNA- and macromolecular-reactive species. A second area concerns the rate of cell duplication, important in leading to cell transformation to an early neoplastic state. The third key area explores agents that bear on a further development and growth of the transformed cells, an area that has quite distinct dose-response relationships from the first type. Therefore, modulation of the third area provides excellent means of control. In addition, of course, the optimal means is avoiding exposure to genotoxic carcinogens.