Improving American Indian cancer data in the Washington State Cancer Registry using linkages with the Indian Health Service and tribal records

The number of IHS-enrolled American Indians or tribal members included in the WSCR would be underestimated by one third in the absence of record linkages, and the estimated cancer incidence of 43.6% would be lower before linkage. It is feasible to obtain tribal-specific cancer rates by linking tribal rolls to cancer registries, although the small number of cases in most tribes is a significant limitation. Further efforts to improve racial classification of American Indians in cancer registries should be undertaken.