Cancer incidence among native Americans of western Washington.

The incidence of cancer among Native Americans in Alaska, Canada, and the south western United States has been reportedly low relative to the Caucasian populations in these areas. We investigated the incidence of cancer among the Native Americans of Western Washington for the time period 1974-1983 and compared it to that of the Caucasian population using two types of analyses, age-standardized incidence ratios (SIR) and proportional cancer incidence ratios (PIR). Native Americans of this area were found to be at lower risk of cancer than Caucasians at almost all ages. The age-standardized incidence ratio (SIR) for all cancer sites was 0.4 (p less than 0.01) for males and 0.6 (p less than 0.01) for females. A relative excess of cancer of the cervix (SIR = 1.6, PIR = 2.1, p less than 0.05) was found among Native American females. Significant deficits were found for corpus uterine cancer among females (SIR = 0.2, PIR = 0.5, p less than 0.05) and cancer of the prostate among males (SIR = 0.2, PIR = 0.5, p less than 0.05). A suggestive increase in the risk of cancer of the gallbladder was discovered for males and females. This is the first report on cancer incidence among Native Americans in Western Washington.