Background: Mortality, incidence, and survival rates are the primary measures used by the National Cancer Institute (NCI) to monitor cancer in the United States. The Surveillance, Epidemiology, and End Results (SEER) data system collects data on all cancers diagnosed among residents in geographically defined populations, which comprise about 10% of the U.S. population. This data system is the major component of the NCI system for tracking these rates. Thus, it is important to assess the degree to which SEER data are representative of the entire U.S. population.
Purpose: National data on mortality, but not on incidence or survival, are available from the National Center for Health Statistics. These data provide a census against which mortality data from the subset of the SEER regions may be compared.
Methods: Multivariate regression analyses of age-adjusted mortality rates from 1975 to 1988, computed for the SEER areas and for the entire United States, were performed for race- and sex-specific data from 15 cancer sites. Representativeness was evaluated by testing for differences in trends and levels between the data from the U.S. population and those from the SEER Program.
Results: Data from the SEER regions reflected the correct direction of trend for all sites, although some race-, sex-, and site-specific differences existed for the magnitude of the trends and levels of mortality when compared with data from the U.S. population.
Conclusions: The demonstration that data from the SEER population do occasionally yield mortality rates that differ from those for the entire U.S. population suggests that data from the SEER coverage population are, in some cases, not representative of the greater U.S. population.
Implications: This issue is of particular relevance to the interpretation of incidence measures, computed from the SEER data, for which there is no national database. Future efforts should be directed at a better understanding of how the SEER population differs from the U.S. population so that SEER rates can be adjusted to be more nationally representative.