Racial differences in cancer incidence: the significance of age-specific patterns.

Racial differences in cancer incidence between black and white populations are examined for leading cancer sites by age at diagnosis. The analysis was based on 116,858 incidents, invasive cancer cases occurring between 1973 and 1982 in black and white, male and female residents of the Detroit metropolitan area. Cases were drawn from the population-based Metropolitan Detroit Cancer Surveillance System. The results indicate that racial differences in age-specific incidence rates for many forms of cancer are more pronounced when cancer occurs in early adulthood and middle age (20 to 44 and 45 to 54 years) than in persons aged 65 and over. This is especially the case for male subjects. This may suggest that blacks and whites who survive to their senior years before developing cancer may be more alike in terms of behavior, exposures, or host susceptibility than blacks and whites for whom cancer occurs in early adulthood or middle age. The etiologic and public health implications of these race and age patterns must be considered in greater detail. Future case-control studies should include sufficient numbers of patients in both the youngest and oldest age groups to ensure that black and white differences can be adequately examined by age at diagnosis.