The epidemiology of cancer.

The epidemiology of cancer has been described as the study of cancer's distribution by age, sex, economic status, etc. and of those factors which determine its prevalence. Twenty-five years ago the mortality rate in Canada for all sites of malignancy was approximately identical for both males and females, but since that time there has been a constant and significant increase in cancer among males; a slight, yet significant, decrease among females.In the past few years mortality from cancer of the respiratory system has shifted from a minor to a major component of cancer mortality. In addition, migration from one country to another changes the cancer risk; patterns of disease among migrants shift substantially to those found in the country to which they have migrated. Cigarette smokers have a higher risk of bladder cancer than non-smokers.The study of occupational exposure to specific chemical and physical agents is potentially one of the most important ways in which analytical epidemiologic methods can contribute to the knowledge of cancer etiology. One of the basic requirements for successful epidemiology programs is the organization of population-based cancer registries which provide the necessary descriptive information on the population.