Female breast, prostate, lung, and colorectal cancers are the leading incident cancers among American Indian and Alaska Native
(AI/AN) and non-Hispanic White (NHW) persons in the US. To understand racial differences, we assessed incidence rates, analyzed trends, and examined geographic variation in incidence by Indian Health Service (IHS) regions.
To assess differences in incidence, we used age-adjusted incidence rates to calculate rate ratios (RRs) and 95% confidence intervals (CIs). Using joinpoint regression, we analyzed incidence trends over time for the four leading cancers from 1999 to 2015.
For all four cancers, overall and age-specific incidence rates were lower among AI/ANs than NHWs. By IHS regions, incidence rates for lung cancer
were higher among AI/ANs than NHWs in Alaska (RR: 1.46; 95% CI: 1.37, 1.56), Northern (RR: 1.29; 95% CI: 1.25, 1.33) and Southern (RR: 1.06; 95% CI: 1.03, 1.09) Plains. Similarly, colorectal cancer
incidence rates were higher in AI/ANs than NHWs in Alaska (RR: 2.29; 95% CI: 2.14, 2.45) as well as Northern (RR: 1.04; 95% CI: 1.00, 1.09) and Southern (RR: 1.11; 95% CI: 1.07, 1.15) Plains. Also, AI/AN women in Alaska had a higher incidence rate for breast cancer
than NHW women (RR: 1.05; 95% CI: 1.05, 1.20). From 1999 to 2015, incidence rates for all four cancers decreased in NHWs, but only rates for prostate (average annual percent change [AAPC]: -4.70) and colorectal (AAPC: -1.80) cancers decreased considerably in AI/ANs.
Findings from this study highlight the racial and regional differences in cancer incidence.