Advancing Education, Research, and Quality of Care for the Head and Neck oncology patient.
Introduction: Socioeconomic disparities in head and neck cancer (HNC) outcomes are well documented across patient populations. However, studies differ in identifying education level, income status, poverty, or other factors as the key socioeconomic status (SES) markers driving HNC outcomes. Furthermore, while traditional SES markers assess an individual’s risk profile, they may fail to capture social and economic diversity within counties. Income inequality may better reflect these variations by highlighting pockets of disadvantage that can amplify health disparities. To the authors’ knowledge, no other study has explored the relationship between income inequality and HNC outcomes.
We hypothesize that income inequality is a stronger predictor of HNC patient outcomes compared to standard SES indicators—household income, poverty level, and education level. Additionally, this study will examine the interaction between income and income inequality in relation to HNC survival.
Methods: De-identified patient outcome data from 2018 is publicly available in the SEER database, including approximately 10,000 adult cases across the U.S. This dataset includes information on stage at presentation, survival (after 60 months), household income, poverty level, and education level. Data for these SES markers were reported per county. Income inequality was quantified using Gini index data collected from the Census Database for all SEER registry counties. Multivariate regression coefficients were compared to assess the predictive value of traditional SES markers and income inequality on 5-year observed survival (outcome variable). Additionally, an interaction effect regression was conducted to determine if combinations of income and income inequality levels were correlated with different HNC outcomes. All independent variables were analyzed in quintiles.
Results: Income inequality was strongly associated with HNC survival and proved to be a stronger predictor of survival than both median household income and poverty level. Compared to those living in the areas with the most equal wealth distribution (Gini quintile 1), counties with greater inequality (Gini quintiles 3, 4, and 5) exhibited survival decreases of 8.1%, 10.3%, and 9.0%, respectively (p<0.0001). There were no statistically significant survival differences between lower and higher SES quintiles for income level, while there was only a 4.1% survival increase (p<0.0222) for counties with the lowest poverty level (quintile 5) compared to the highest poverty counties (quintile 1). Moreover, interaction effect results revealed that although income level alone was a poor survival predictor, counties with both the lowest income and lowest income equality showed significantly worse survival outcomes compared to counties with the highest median household income and highest income equality (18.5% survival difference, p<0.0001).
Discussion: Income inequality appears to be a more robust indicator of outcomes of head and neck cancer care than income level or poverty level, as it may reflect the unequal distribution of resources within counties. While income level alone did not correlate with survival, combining income with income inequality helped further stratify community risk, identifying those disproportionately at risk. By considering income inequality as a key factor in identifying high-risk communities, public health efforts can better target vulnerable populations with focused interventions and resources, potentially reducing disparities and improving overall HNC outcomes.