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

Abstract

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. 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. 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. 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.