Radiation initiation of carcinogenesis in vivo: A rare or common cellular event

A major goal in the area of carcinogenesis research is to estimate the risk to individuals and populations from exposure to environmental carcinogens. In most cases, an individual's exposure level is very low. For example, the relevant environmental dose of ionizing radiation is in the range of milligray (0.1 rad). An estimation of either the risk or the shape of the dose-response curve in this dose range is virtually impossible to obtain directly from either human epidemiology or relevant experimental models. An alternative approach is to estimate the shape of the dose-response curve based on consideration of the cellular events and mechanisms involved in carcinogenesis. The number of cells that are involved in the initiation stage of radiation or chemical carcinogenesis will have a major influence on the shape of the dose-response curve for these agents. The authors explore this question by analyzing data taken from the field of experimental radiation carcinogenesis. The conclusions, however, also apply to environmental chemical carcinogenesis