Cancer mortality and geographic inequalities: a detailed descriptive and spatial analysis of social determinants across US counties, 2018–2021

Objective: In the United States, cancer mortality rates continue to decline, yet geographic and racial disparities persist and are particularly evident in the Delta region, characterized by high economic distress and disease burden. We examined cancer mortality patterns by demographic groups across geographic region (Delta vs non-Delta) and investigated the influence of macro-level social determinants of health (SDoH) in cancer death. Study design and methods: This observational study included cancer death records of individuals aged ≥20 years from 2018 to 2021 in the United States. County-level characteristics were ascertained through the linkage of multiple national administrative and community surveys. We estimated age-standardized mortality rates (ASR) and rate ratios. We calculated the adjusted relative risks by county-level SDoH (geographic region, rurality, household income, income inequality, health insurance, and education) and other factors using age-adjusted multivariate quasi-Poisson regression. Results: In 2018–2021, approximately 2.4 million cancer deaths occurred in the United States. We observed important declines in the Black-White disparities, from 16.6% in 2018 (ASR = 289.9 vs 248.6 per 100,000) to 12.1% in 2021 (281.1 vs 250.8) in the Delta region and from 15.9% (254.9 vs 219.9) to 10.7% (240.6 vs 217.3) in the non-Delta region, though Black men in the Delta region remained the highest rate (ASR₂₀₂₁ = 346.9 per 100,000). County-level analyses provided strong evidence of geographic inequality and the role of SDoH, particularly education and income inequality. Conclusions: Unfavorable SDoH are associated with increased cancer death risk. Region-specific health policies and interventions in the Delta region are essential to advance cancer health equity.