COLORECTAL-CANCER INCIDENCE AND SURVIVAL AMONG ALASKA NATIVES, 1969-1993

Background Although colorectal cancer rates are low among most groups of Native Americans in North America, rates for Alaska Natives have be en substantially elevated compared with US rates for all races combine d. Methods To better describe the epidemiology of colorectal cancer in cidence and survival among Alaska Natives, stratified by gender and tr ibal/ethnic affiliation, we examined data collected by the Alaska Nati ve Cancer Registry 1969-1993. We calculated age-adjusted and age-speci fic incidence as well as actuarial survival rates, and examined histol ogical type, site, stage at diagnosis, and treatment. We compared thes e data to colorectal cancer data from whites living in western Washing ton. Results In all, 587 colorectal cancer cases were identified among Alaska Natives over the 25-year period, fur an age-adjusted annual in cidence rate of 71.4/100 000 in women, and 69.3/100 000 in men. Compar ed to Alaska Indians, colon cancer rates were significantly higher in Aleuts (relative risk [RR] = 1.6, 95% CI : 1.2-2.2) and in Eskimos (RR = 1.5, 95% CI : 1.2-1.8), while rectal cancer rates did not differ by race/ethnicity. Alaska Natives experienced a 50% higher incidence sat e of colorectal cancer overall compared to western Washington whites ( RR = 1.5, 95% CI : 1.3-1.6), although rectal cancer rates were similar in the two populations. The highest RR were seen among Alaska Native women; Aleuts and Eskimos had colon cancer rates more than twice that of western Washington white women. No unusual qualitative features wer e found in the cancers occurring in Alaska Natives. Actuarial colorect al cancer survival rates for Alaska Natives overall were 74% at one ye ar and 42% at 5 years; these rates were very similar to those observed for the western Washington population. Both one and 5-year survival r ates showed a significant trend towards improvement over time. Conclus ions Alaska Natives had substantially higher colorectal cancer inciden ce rates compared to western Washington whites. Rates were particularl y high for Aleut and Eskimo women. These data suggest a need for inten sified secondary prevention strategies for this high-risk population, while further research is needed to identify modifiable risk factors.