Cancer stage at diagnosis, treatment, and survival among American Indians and non-American Indians in Montana.

BACKGROUND: The intent of the current study was to ascertain whether differences in cancer survival between Montana non-American Indians (non-AI) and Montana American Indians (AI) were related to differences in stage of disease at diagnosis or in the type of treatment received. METHODS: A case-control design was utilized using data from the Montana Central Tumor Registry and the Indian Health Service medical records . AIs diagnosed between January 1, 1984 and December 31, 1993 were the cases in the study, and non-AIs diagnosed in the same period were the controls. Chi-square tests and life table techniques were used to analyze the data. RESULTS: Five hundred twenty -two cases were matched with controls. The 5-year cancer survival rate for AIs was 36% and was 47% among non-AIs. The stage at the time of diagnosis was local in 34 % of AIS and 36% of non-AIs. The stage was regional in 30% of AIs and 26% of non-AIs . Distant disease at the time of diagnosis was present in 25% of AIs and 24% of non -AIs, whereas an unknown extent of disease was present in 11% of AIs and 14% of non -AIs. AIs underwent surgery less frequently than non-AIs (79% vs. 86%), but this did not appear to contribute to the survival differences observed. CONCLUSIONS: The survival differences observed in the current study cannot be explained easily by differences in the cancer stage at diagnosis or the type of treatment received. CI - Copyright 2000 American Cancer Society.