Identification of cancer risk factors and potential prevention strategies have been some of the most important medical and research contributions to the improvement of public health in the past half-century (Steele 2003). Und- standing the role of lifestyle, exposure to endogenous factors and exogenous environmental factors, and individual genetic and epigenetic variability have contributed significantly to this effort. Cancer prevention strategies have been developed based on results of epidemiologic, preclinical, and clinical studies that have generated clues for identifying risk factors that may be modulated by changes in lifestyle, such as smoking cessation or dietary modification (Greenwald 2002a). In addition, significant progress in medical interventions involving chemoprevention-a pharmacological approach to intervention that aims to prevent, arrest, or reverse either the initiation phase of carcinogenesis or the progression of premalignant cells-is beg- ning to pay dividends in reducing risks associated with cancer.Emerging technologies, identification of biomarkers of risk, and advances in genetics research also are finding applications in chemoprevention research that p- mise to speed the acquisition of knowledge on the molecular and cellular - fects of chemopreventive agents. 2 Lifestyle Approaches Population studies from the 1950s through the early 1980s provided c- pelling evidence that modifiable lifestyle choices can either increase or - crease cancer risk. For example, several landmark epidemiologic studies in the 1950s showed a clear association between smoking and lung cancer (Wynder and Graham 1950; Levin et al. 1950). In 1964, the U. S.
