Cancers as ecosystems: From cells to population

Epidemiology studies the causes of cancer. Through this research it identifies modifiable risk factors that may be amenable to interventions to prevent cancer. Here I review the focus on proximate causes that drive cancer risk and identify the general lack of detailed study of more distal or up-stream factors that influence the behaviors and exposures within society. The social ecologic model places individual (and cells within individuals) in the broader context of community and social policies that modify exposures and hence cancer risk more broadly. Examples are drawn from and range of exposures and risk of breast and cervical cancer. Evolving focus of epidemiology incorporates biomarkers to refine exposure measures and define pathways from exposure to cancer etiology. To date these markers often include DNA, inflammatory markers, nutrients, and so forth. Indicators of biologic processes at the cellular level such as stroma and structures around the cells of origin for cancer have not been included.