Generalizability of the surveillance, epidemiology, and end results registry population: factors relevant to epidemiologic and health care research.

To assess the generalizability of the population included in the Surveillance, Epidemiology, and End Results (SEER) tumor registries to the overall United States population, we compared the population of the 198 SEER counties to the population of the 2882 non-SEER counties regarding sociodemographic factors, physician availability, and availability of pertinent hospital resources. The population residing within the SEER areas is more affluent, has lower unemployment, and is substantially more urban than the remainder of the U.S. population (p < 0.001 for each). The SEER areas have fewer general and family practice physicians, but more total nonfederal physicians, general internists, and specialists relevant to cancer care. SEER areas have fewer Joint Commission on Accreditation of Hospitals accredited hospitals, hospital beds, and hospitals with CT scanners, but more hospitals with bone marrow transplantation. The differences between the SEER population and the remainder of the United States, especially SEER's higher socioeconomic status and more urban population, should be considered when generalizing from SEER to the entire country.