Bottom Line: Compared with the non-Hispanic white (NHW) population, the urban American-Indian and Alaskan Native (AIAN) community was more likely to have lower survival rates following invasive prostate and breast cancer.
Journal in Which the Study was Published: Cancer Research, a journal of the American Association for Cancer Research
Authors: Lead author Marc A. Emerson, MPH, PhD candidate, Department of Epidemiology, University of North Carolina at Chapel Hill and senior author Laurel A. Habel, PhD, associate director for cancer research at the Kaiser Permanente Northern California (KPNC) Division of Research
Background: “It’s been reported that the AIAN community has a higher cancer burden than other racial/ethnic groups,” said Emerson, who was an Intramural Research Training Award fellow in the Division of Cancer Control and Population Sciences at the National Cancer Institute while conducting this work. “However, accurate, population-based information on the cancer experience for this population residing in an urban setting is severely lacking.”
Previous AIAN data regarding cancer incidence and mortality are linked with the Indian Health Service (IHS); however, access to IHS facilities for the majority of AIANs is limited, as IHS clinics and hospitals are located near reservation lands, Emerson explained. Additionally, only members of federally recognized AIAN tribes qualify for treatment by the IHS. Altogether, it is estimated that up to 80 percent of the AIAN population cannot utilize IHS services, resulting in data acquisition that is not representative of the entire cohort, he said.
How the Study Was Conducted and Results: This study analyzed data from 582 AIAN and 82,696 NHW enrollees of KPNC, a health care system that covers roughly one-third of people living in the Bay Area and Central Valley in California. Participants were diagnosed with primary invasive breast, prostate, lung, or colorectal cancer between January 1997 and December 2015. As enrollees of the same comprehensive health plan, participants of this study had approximately equal access for both cancer treatment and preventative services. However, AIANs had a somewhat higher comorbidity burden as compared to NHWs.
“The AIAN population has a unique history of social, environmental, and cultural injustices that have impacted health,” noted Emerson. “As a result, many of these long-term exposures have resulted in an unequal contemporary burden of comorbid health conditions.”
In addition to comorbidity burden, Habel and colleagues compared cancer survival between the AIAN and NHW populations. They found that the AIAN community had an 87 percent increased risk for prostate cancer-specific mortality, and a 47 percent increased risk for all-cause mortality following invasive breast cancer, after controlling for patient factors, disease characteristics, and comorbidity status. Additional adjustment for income did not significantly change the outcomes. They did not observe higher overall or cancer-specific mortality for AIAN individuals with lung or colorectal cancer.
Author’s Comments: “Our results suggest that factors other than health insurance and income may play a role in the survival differences observed for breast and prostate cancer,” said Emerson. “These factors could include differences in tumor biology or differences in aspects of treatment, such as adherence.”
Future studies on the tumor biology of cancers in the AIAN population and on adherence to cancer treatments could help better understand and address the disparities, Emerson said.
Study Limitations: Limitations of the study include an inability to control for quality of care, adherence, or lifestyle factors that may vary across racial subgroups. “The electronic health records do not have data on some lifestyles and behaviors that may have influenced cancer outcomes,” Habel noted.