Impact of Comorbidities on Survival among American Indian and Alaska Native People with Cancer: A Surveillance, Epidemiology, and End Results (SEER)-Medicare Study

BACKGROUND: American Indian and Alaska Native (AIAN) people experience lower cancer survival than other racial/ethnic groups for several cancer sites. We explored predictors of cancer survival among AIAN people, with a specific focus on the potential impact of comorbidities. METHODS: We analyzed Surveillance, Epidemiology, and End Results (SEER)-Medicare linked data. AIAN people diagnosed with breast (female only), lung, and colorectal cancers from 2000-2019, aged 66+ years at diagnosis, and with at least one year of Medicare coverage prior to diagnosis were included in the study. We used multivariable-adjusted Cox proportional hazards models to assess associations of comorbidity class, previously defined using latent class analysis, with overall and cancer-specific survival, adjusted for sociodemographic characteristics and area-based social measures. RESULTS: The sample included 831 individuals with female breast cancer, 1009 individuals with colorectal cancer, and 1195 individuals with lung cancer. Comorbidity class was associated with five-year hazard of death from any cause for breast and colorectal cancer, but not lung cancer patients. Further, we only observed associations of comorbidity class with five-year cancer-specific death for lung cancer, where the class associated with heart and vascular-related conditions experienced increased hazard of death. CONCLUSIONS: Higher comorbidity prevalence among AIAN people compared to other racial/ethnic groups did not contribute to observed disparities in cancer-specific survival; however, AIAN people with comorbid conditions may be more likely to experience death from any cause than those without these conditions. IMPACT: Differences in prevalence of comorbid conditions are unlikely to drive disparities in cancer-specific survival observed among AIAN peoples.