Statistical data shows that American Indian and Alaska Native population faces a higher risk of getting one of many cancers than non-Hispanic, white Americans. A study funded by the Centers for Disease Control and Prevention (CDC) and published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research, also shows that this higher risk is also associated with considerable variation among regional groups.
“Our data show that these cancers including lung, liver, kidney, colorectal and stomach cancers,” Stephanie C. Melkonian, Ph.D, an epidemiologist at the Centers for Disease Control and Prevention (CDC), Division of Cancer Prevention and Control.
“Cancer incidence rates for many cancers also differ by geographic area,” she added.
Geographic differences in cancer rates may be due to environmental, behavioral, or socioeconomic factors that differ for each group by area. However, most U.S. cancer statistics present American Indians and Alaska Natives as one large group.
“Nationally aggregated data presents an incomplete picture because it obscures geographic differences in cancer incidence rates,” Melkonian explained, who is also the lead author of the published study.
Incidence rates and trends
To further examine cancer incidence rates and trends within the American Indian and Alaska Native population, Melkonian and colleagues assessed data from the CDC’s National Program of Cancer Registries and the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program from the years 2010-2015.
They restricted their analyses to areas known as purchased/referred care delivery area counties, which encompass or are adjacent to federally recognized tribal lands. Approximately 53% of the U.S. American Indian and Alaska Native population lives in one of these counties.
The researchers linked data from these cancer registries to Indian Health Services patient registration databases to identify cancer cases in the American Indian and Alaska Native population in six geographic areas including the Northern Plains, Alaska, Southern Plains, Pacific Coast, East, and Southwest regions.
Among men, the study showed that liver cancer was more than twice as common in the American Indian and Alaska Native population than in whites. Kidney and stomach cancer incidence was significantly higher for American Indian and Alaska Native population men than white men in four out of six American Indian and Alaska Native population regions.
Among women, liver cancer incidence was more than three times higher for the AI/AN population than for whites. American Indian and Alaska Native population women also had higher rates of lung, colorectal, kidney, cervical, and stomach cancer.
The study also showed significant increases in incidence rates for many of these cancers over time. Liver cancer increased 3.3% annually for American Indian and Alaska Native population males and 4.5% annually for American Indian and Alaska Native population females between the years 1999-2015. During this time, kidney cancer rates increased 2.4% and 1.6% annually for American Indian and Alaska Native population males and females, respectively.
While colorectal cancer incidence rates decreased by 1.1% annually for American Indian and Alaska Native population males, there were no observed decreases for AI/AN females. Breast cancer incidence rates increased by 0.9% annually in American Indian and Alaska Native population females.
The differences in overall cancer incidence rates between American Indian and Alaska Native population and white populations have grown over time.
“The data shows that the prevalence of certain cancer risk factors varies geographically, and is higher in the American Indian/Alaska Native population in some regions. Some important cancer risk factors include obesity, commercial tobacco use, and viral hepatitis,” Melkonian noted.
“However, some of the regional differences we discovered through our updated data were of most interest.”
Other key regional differences:
- Despite decreasing trends in colorectal cancer incidence, rates of colorectal cancer were higher in the American Indian and Alaska Native population population in most regions, with the highest being in the Northern Plains, Southern Plains, and Alaska.
- Overall breast cancer rates were lower for American Indian and Alaska Native population women than for white women, however, significant variation occurred across the country. The East, Southwest, and Pacific Coast had much lower breast cancer rates for American Indian and Alaska Native population women, while Alaska and the Southern Plains had considerably higher rates than white women.
- Gastric cancer, which is more common in the American Indian and Alaska Native population population than in the overall U.S. population, had more elevated rates in the Southwest and Alaska. Melkonian said H. pylori infection is a leading risk factor for gastric cancer.
Understanding regional variations
Melkonian said the study indicates the importance of studying regional variations in cancer incidence in the American Indian and Alaska Native population in order to ensure a complete understanding of these groups’ cancer burden and identify where to implement targeted public health action.
“These data can guide us on how to design tailored interventions to screen for and prevent many of these common cancers,” she said.
Melkonian noted that one limitation of the study is the potential for misclassification of American Indian and Alaska Native populationstatus. Also, American Indian and Alaska Native population individuals living in urban areas may be underrepresented in the data.
Melkonian SC, Jim MA, Haverkamp D, Wiggins CL, McCollum J, White MC, Kaur JS, Espey DK. Disparities in Cancer Incidence and Trends among American Indians and Alaska Natives in the United States, 2010–2015. Cancer Epidemiol Biomarkers Prev 2019;28:1604–11. [Article]