Cancer epidemiology: shortcomings and possibilities.

The development of the concepts of initiators and promoters in carcinogenesis necessitates deliberations of evidence from human cancer epidemiology. Recent arguments in favor of mortality data as a more reliable indicator of trends in cancer incidence than morbidity data collected from cancer registries are disputed. Inconsistency in the use of data is pointed out. Comparisons of data from cancer registration in Denmark with those from Connecticut and upstate New York show such congruity that it is impossible to accept suggestions of systematic bias of significance without direct evidence to that effect. Since accurate information on periods of exposure and on the onset of disease is fundamental to considerations of initiators and promoters the following proposals are made. Payrolls or similar data should be kept safe for 40 years for occupations where exposure to carcinogens may be suspected. Experience on latent periods from the last 100 years should be systematically reassured. Death certificates showing a diagnosis of malignant neoplasia should always state the histological diagnosis if any.