Clinical studies of cancer etiology

Clues to causes of cancer in man can be identified through clinical observation of patients. Alert practitioners have, for example, recently discovered carcinogenic effects of occupational exposure to vinyl chloride and of diethylstilbestrol therapy during gestation. Clinical case studies have also clarified the role of host susceptibility in development of cancer. In most instances, validity of initial clinical observations was established by more detailed epidemiologic and laboratory studies. Clinicians can contribute to carcinogenesis studies by being alert to causes of cancer in their patients, and by referring exceptional observations to clinical epidemiologists and basic scientists for further study. Knowledge of risk factors can be applied to cancer prevention and early detection.