Thousands of Excess Cancers Among American Indians/Alaska Natives, Especially in Southern Plains

By Marilynn Larkin

October 30, 2020

NEW YORK (Reuters Health) - Liver, stomach, kidney, lung, colorectal and female breast cancers have a higher incidence rate among American Indian/Alaska Native (AI/AN) populations compared with non-Hispanic Whites, with the largest number of excess cancers occurring in the Southern Plains region, a new study shows.

"Other researchers may learn from our research efforts by understanding that we are refining the accuracy of U.S. cancer statistics by considering geographic differences in the cancer incidence rates of AI/AN populations," Dr. Stephanie Melkonian of the U.S. Centers for Disease Control and Prevention in Albuquerque, New Mexico told Reuters Health by email. "Previously, the majority of U.S. cancer statistics presented AI/AN populations as one group using nationally aggregated data."

Dr. Melkonian and colleagues studied incident AI/AN cancer cases diagnosed between 2012-2016 and compared them to cases among non-Hispanic Whites.

Overall, they report in the American Journal of Epidemiology, liver, stomach, kidney, lung, colorectal and female breast cancers had higher incidence rates among AI/AN populations across most regions. Nearly 5,200 excess cancers occurred, with the largest number of excess cancers occurring in the Southern Plains region.

More specific findings included the following:

- Among AI/AN males, the leading sites with elevated incidence were liver, stomach, kidney, colorectal, myeloma, and lung; sites for females were similar, except for melanoma, and including cervical cancers.

- Rate ratios ranged from 1.09 (lung) to 2.37 (liver) among AI/AN males and 1.06 (lung) to 3.03 (liver) among AI/AN females. The incidence rates were higher among AI/AN males compared to females, ranging from 23% higher for lung cancer, to 129% higher for liver cancer.

- Among AI/AN males, the number and type of cancers with elevated incidence varied by region, led by Alaska, the Southern Plains, Southwest, and the Northern Plains; rate ratios ranged from 1.14 (colorectal cancer in the Southwest) to 4.36 (stomach cancer in Alaska).

- Among AI/AN females, the Southern Plains, Northern Plains, Alaska, and the Pacific Coast had the most types of cancer with elevated incidence; rate ratios ranged from 1.15 (corpus and uterus in the Pacific Coast) to 4.07 (stomach in Alaska).

Dr. Melkonian said, "Addressing cancer disparities is complex; however, one possible avenue is through community programs and partnerships that are linked with clinical services. Community health aides and patient navigators can potentially help community members access and understand the preventive care they need to make sure they get the right care at the right time."

"Some of these efforts might include promoting healthy environments and addressing underlying social determinants of cancer risk, including access to care, food insecurity, and transportation," she added. "Community-based interventions to support healthy behaviors and promote recommended screening for cancer, or its risk factors, may also reduce cancer disparities for AI/AN populations."

Dr. Eyal Meiri, Interim Chief of Medical Oncology and member of the GI Cancer Center at Cancer Treatment Centers of America in Atlanta, commented by email to Reuters Health, "These findings are not surprising. Disparities in the incidence of adult-acquired cancers reflect lifestyle and socioeconomic factors that seed development of the cancers described in this study - unlike genetically inherited or younger adult cancers."

"For example," he said, "we know obesity, diabetes, alcohol, tobacco and diets that are high in fat, low in fiber and lack fresh fruit and vegetables are drivers for elevated risk of colorectal cancer. According to the study, all of these risk factors have a higher incidence in AI/ANs. Disparities in this area can be corrected by fostering lifestyle changes and socioeconomic opportunity to improve these high-risk behaviors."

"Liver cancer is associated with any underlying liver toxin. Hepatitis C and alcoholism are known risk factors and are prevalent in the AI population," he said. "However, just as we can reduce the incidence of cervical cancer by administering vaccination for HPV, we can screen for and treat hepatitis C. Alcoholism, on the other hand, may be best addressed at the community level."

"Socioeconomic disparity contributes to cancer incidence," he said. "Underlying factors include limited access to proper health care and nutrition, isolated environments that contribute to high-risk behaviors, and poor educational opportunities - all very disheartening amid our current turmoil."

SOURCE: American Journal of Epidemiology, online October 14, 2020.