Cancers of the urinary tract among American Indians and Alaska Natives in the United States, 1999-2004

BACKGROUND: Assessment of the kidney parenchyma ("kidney") and urinary bladder ("bladder") cancer burden among American Indians and Alaska Natives (AI/AN) has been limited. Using a database with improved classification for AI/AN, the authors described patterns of these 2 cancers among AI/AN and non-Hispanic whites (NHW) in the United States. METHODS: Cases diagnosed during 1999 to 2004 were identified through National Program of Cancer Registries and the Surveillance, Epidemiology and End Results program and linked to the Indian Health Service (IHS) registration records. Age-adjusted incidence rates, rate ratios (RR), annual percent change, and stage at diagnosis were stratified by IHS Contract Health Service Delivery Area (CHSDA) counties to adjust for misclassification. RESULTS: Kidney cancer incidence among AI/AN in CHSDA counties exceeded that among NHW (RR, 1.51; 95% confidence interval CI, 1.42-1.61), and was highest among AI/AN in the Northern Plains, Southern Plains, Alaska, and Southwest. Average annual increases were highest among AI/AN (5.9%) and NHW (5.9%) males aged 20 to 49 years, although statistically significant only among NHW. Conversely, bladder cancer incidence was significantly lower among AI/AN than NHW (RR, 0.40; 95% CI, 0.37-0.44). For both sites, AI/AN were significantly less likely to be diagnosed at an earlier stage than NHW. CONCLUSIONS: AI/AN have about 50% greater risk of kidney cancer and half the risk of bladder cancer than NHW. Although reasons for these enigmatic patterns are not known, sustained primary prevention efforts through tobacco cessation and obesity prevention are warranted.