November 15, 2007 / Volume 110 / Number 10
ing IHS and cancer registry data and restricting anal- yses to CHSDA counties reduces AI/AN misclassifica- tion and improves on the accuracy of cancer incidence data previously reported for AI/AN. The report also includes data from 30 state cancer regis- tries and is more representative nationally of the AI/ AN population than previous reports.
Findings from this study, as well as prior reports from specific regions or registries26,89–92 or from mor- tality data,32,34 indicate that wide regional variation is characteristic of AI/AN cancer surveillance and that region-specific data are essential to characterize the AI/AN cancer burden. In general, cancer rates among AI/AN persons were highest in Alaska and the Northern and Southern Plains and lowest in the Southwest. The wide regional variations in cancer rates may reflect in part geographic variations in screening and in risk factors, such as tobacco use (lung, kidney, and colorectal cancer), obesity (color- ectal and breast cancer), low level of physical activity (breast and colorectal cancer), heavy alcohol con- sumption (breast and liver cancer), and dietary fac- tors, including consumption of large amounts of red meat and inadequate intake of fruits and vegetables (colorectal cancer). Research designed to elucidate regional variations in risk factors may help identify appropriate prevention and control strategies.
The regional patterns of lung cancer rates mirror the regional smoking prevalence from BRFSS, as noted in this report and elsewhere.35 Although smok- ing prevalence in AI/AN respondents in the South- west is similar to that of NHW respondents, AI/AN smokers in the Southwest tend to smoke fewer cigar- ettes per day compared with non-AI/AN smokers and AI/AN smokers in other regions.93,94 Predictably, lung cancer incidence rates for the AI/AN population in the Southwest were lower than the rates among for the NHW population during the period of this report, a pattern that was documented previously95,96 and that reflects the lower rate of cigarette consump- tion.93,97,98 Nonetheless, radon exposure during ura- nium mining caused a disproportionate number of lung cancer cases among AI/AN men in this region in the 1970s and 1980s99,100; the proportion of lung cancer cases attributable to uranium-related expo- sure in the past decade currently is unknown but remains a concern in this region.
Smoking also has been associated with an increased risk of developing101 or dying102 from col- orectal cancer and of being diagnosed at an earlier age.103 Furthermore, there is mounting evidence of an association between Type 2 diabetes and colorec- tal cancer,104,105 including a positive interaction of smoking on this risk.106 The prevalence of Type 2 di-
abetes is generally higher in AI/AN persons, is grow-
and exhibits regional differences35,108
it is high in the Northern Plains and the Southwest and low in Alaska, where, although it is lower, the
prevalence is increasing at a rapid rate.109
colorectal cancer screening prevalence is low in the NHW population and is lower still in the AI/AN population except for endoscopic screening preva- lence in the East and Alaska, where rates for the AI/ AN populations are similar to those for the NHW populations. The parity in endoscopic screening between AI/AN and NHW persons in Alaska may reflect efforts in that state to increase screening for the AI/AN population110,111 and also may reflect con- cerns that use of FOBT may yield false-positive results in a population with high prevalence of Heli- cobacter pylori (H. pylori) infection.112 This finding also is consistent with the observation of a higher probability of early-stage diagnosis for colorectal cancer in that region from this report.
Breast cancer incidence rates in AI/AN women were lower than for NHW women overall. Although the rate for AI/AN women was similar to the rate for NHW women in Alaska, it was nearly 3 times the rate of AI/AN women in the Southwest. Similar variations have been reported previously and may be because of differences in reproductive or behavioral risk fac- tors or variations in mammography rates.91 Data regarding variations in reproductive characteristics among AI/AN women by region are limited, however. One study reported no differences in age at first birth among women receiving mammograms in IHS or tribal clinics in Alaska, where incidence rates are relatively high, compared with similar women in Ari- zona, where incidence rates are is low.113 Although it has been postulated that the recent decline in breast cancer incidence in the general population is because of the decline in use of HRT, no data are available on HRT use in AI/AN women. Higher rates of mammography in Alaska may be associated with higher breast cancer incidence rates.
AI/AN persons have higher rates of cancers of the kidney and gallbladder than other populations. In this report, rates for kidney cancer were generally higher in AI/AN than NHW populations, especially in the Northern and Southern Plains and the Southwest. The recognized risk factors for kidney cancer—smok- ing and obesity—account for 20% to 30% of renal cell cancers in the U.S.114 Other potential risk factors include hypertension and end-stage renal disease, the prevalence of which is 3 times greater in AI/AN than NHW populations. 115 116
Gallbladder cancer is elevated in AI/AN men and women for all regions combined; however, the cur-