Persistent poverty and breast cancer incidence by tumor subtype: intersections of rural/urban residence and race within USA Surveillance Epidemiology and End Results Registries, 2017 to 2021.

PURPOSE: Breast cancer characteristics and outcomes vary by tumor subtype, poverty, race, and geography. Persistent poverty (> 20% residents in poverty for 30+ years) has been associated with breast cancer risk, but whether associations differ by subtype is unknown. We examined subtype-specific breast cancer incidence by persistent poverty, stratified by rurality and race.

METHODS

Using county-level Surveillance, Epidemiology, and End Results data from 2017 to 2021 (excluding 2020), we calculated Luminal A, Luminal B, HER2-enriched, and triple-negative breast cancer (TNBC) incidence rates. We estimated rate differences (RDs) by persistent poverty using age-adjusted and multivariable linear regression models, with stratification by rurality and county racial composition.

RESULTS

In age-adjusted models, persistent poverty counties had lower incidence of Luminal A (RD - 13.58, 95% CI = - 19.8, - 7.4) and higher TNBC (RD = 3.82, 95% CI = 2.0, 5.6) compared to non-persistently poor counties. Differences were not significant in multivariable models. In stratified analysis, higher TNBC rates were observed in persistently poor rural (multivariable RD =1.70, 95% CI = 0.3, 4.8) but not urban (multivariable RD = - 1.07, 95% CI = - 4.7, 2.5; pint = 0.09) areas. In counties with > 5% non-Hispanic Black population, Luminal B rates were lower in persistently poor vs. non-persistently poor counties (multivariable RD = - 3.96, 95% CI = - 6.7, - 1.2; pint = 0.03).

CONCLUSION

Results from this study suggest that differences in breast cancer subtypes by persistent poverty status are largely explained by other measures of more recent disadvantage including recent poverty, unemployment, uninsurance, and race. Targeted strategies are needed to address breast cancer disparities within socioeconomically disadvantaged communities.