Screening Prevalence and Incidence of Colorectal Cancer Among American Indian/Alaskan Natives in the Indian Health Service

BACKGROUND: Studies on colorectal cancer (CRC) screening and incidence among American Indian/Alaska Natives (AI/AN) are few. AIMS: Our aim was to determine CRC screening prevalence and to calculate CRC incidence among AI/AN receiving care within the Indian Health Service (IHS). METHODS: A retrospective cohort study of AI/AN who utilized IHS from 1996 to 2004. AI/AN who were average-risk for CRC and received primary care within IHS were identified by searching the IHS Resource Patient Management System for selected ICD-9/CPT codes (n = 142,051). CRC screening prevalence was calculated and predictors of screening were determined for this group. CRC incidence rates were ascertained for the entire AI/AN population ages 50–80 who received IHS medical care between 1996 and 2004 (n = 283,717). RESULTS: CRC screening was performed in 4.0% of average-risk AI/AN. CRC screening was more common among women than men (RR = 1.6, 95% CI 1.4–1.7) and among AI/AN living in the Alaska region compared to the Pacific Coast region (RR = 2.5, 95% CI 2.2–2.8) while patients living in the Northern Plains (RR = 0.4, 95% CI 0.3–0.4) were less likely to have been screened. CRC screening was less common among patients with a greater number of primary care visits. The age-adjusted CRC incidence among AI/AN ages 50–80 was 227 cancers per 100,000 person-years. CONCLUSIONS: CRC was common among AI/AN receiving medical care within IHS. However, CRC screening prevalence was far lower than has been reported for the U.S. population.