Introduction: Cancer incidence and mortality rates for American Indians in the Northern Plains region of the United States are among the highest in the nation. Reliable cancer surveillance data are essential to help reduce this burden; however, racial data in state cancer registries are often misclassified, and cases are often underreported.
Methods: We used a community-based participatory research approach to conduct a retrospective ascertainment of cancer cases in clinic medical records over a 9-year period (1995-2003) and compared the results with the state cancer registry to evaluate missing or racially misclassified cases.