Cancer Etiology

Abstract

The etiology of cancer rests not only on an understanding of the biologic processes involved in the disease, but also on epidemiologic evidence of these processes. The evidence falls into two major categories. The first, which could be denoted “circumstantial”, is derived from the interpretation of observed differences in the incidence of certain cancers by sex, age, socioeconomic, and geographic patterns. These include changes in risk upon migration and over time, as well as correlations of cancer risk with other variables (e. g., population density, air pollution, etc.). Whereas a set of observations might be interpreted in more than one way, any theory as to cause must be consistent with the observed distribution if it is to be credible.