Members of the urban American-Indian and Alaskan Native (AIAN) community are more likely to have lower survival rates following invasive prostate and breast cancers when compared to non-Hispanic whites (NHWs), according to a study published in Cancer Research.
The study focused on data from more than 3.9 million members of Kaiser Permanente Northern California (KPNC) and was led by Marc A. Emerson, MPH, from the Division of Cancer Control and Population Sciences at the National Cancer Institute in Bethesda, Maryland, along with researchers from Kaiser Permanente in Oregon and California.
“Despite approximately equal access to preventive services and cancer care in this setting, we found higher mortality for AIAN than NHW [patients] with some cancers, and a greater proportion of AIAN cancer patients with multiple comorbid conditions,” the investigators reported.
AIANs have the lowest 5-year cancer survival (55.5%) in the US when compared to all other races/ethnicities, although the reasons have not been fully investigated. Most information is obtained from population-based cancer registries and racial misclassification is thought to be a problem, even when data are linked with Indian Health Service (IHS). Moreover, up to 80% of American-Indian and Alaskan Natives do not have access to IHS, and cancer treatment is not available at all IHS facilities.
In this retrospective cohort study, 582 AIANs and 82,696 NHWs from the KPNC tumor registry (KPTR) were identified and compared with respect to all-cause mortality as well as cancer-specific mortality in prostate, breast, lung, and colorectal cancer. The KPTR provided data on diagnosis, age at diagnosis, tumor size, tumor grade, stage, and first course cancer treatment (eg, surgery, radiation). Race and ethnicity were primarily self-reported.
A higher proportion of AIAN patients had colorectal cancer, were younger, and had diabetes than NHW patients. The two most common comorbidities at diagnosis were chronic obstructive pulmonary disease and diabetes. A slightly greater proportion of AIANs with any cancer had one or more comorbid conditions when compared with NHWs.
The localized cancer stage distributions between the groups were similar for prostate, breast, lung, and colorectal cancers.
Among patients with breast and prostate cancers, all-cause and cancer-specific mortality rates were higher for the AIAN population compared with NHW; hazard ratios were not decreased when adjusting for comorbidity.
AIAN men had nearly twice the prostate cancer-specific mortality risk compared with NHW men. Similarly, breast cancer all-cause mortality risk for AIAN women was 47% greater than for NHW women. In contrast, risks of lung cancer or colorectal cancer were similar between the groups.
“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 Mr. 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. “These factors could include differences in tumor biology or differences in aspects of treatment, such as adherence.”
The investigators cautioned that the study had a number of limitations. It did not control for racial differences in quality of care, treatment compliance, or lifestyle factors across the groups. In addition, the study population was comprised of insured members of one integrated health plan, and linking with central cancer registries could quantify racial misclassifications. The AIAN community is also classified as one group, which may limit tribe-specific results.
“In our study of 582 AIAN [patients] with cancer in an integrated health care system, where enrolled patients have approximately equal access to cancer care services, we found that prostate all-cause and cancer-specific survival and breast cancer all-cause survival among AIAN were significantly lower compared with NHW,” the authors concluded. “Specifically, after adjustment for disease characteristics and comorbidities, prostate cancer–specific mortality among AIAN men was 87% higher than among NHW and the all-cause breast cancer mortality among AIAN women was 47% higher than among NHW.”
To read more about this study, click here.