60 Racialized Economic Segregation as a Mediator of Racial Disparities in Triple-Negative Breast Cancer

Background

Black women experience disproportionately high rates of triple-negative breast cancer (TNBC), an aggressive subtype with limited targeted therapies. The extent to which structural racism and health insurance disadvantage mediate this disparity remains unclear.

Materials and Methods

This study obtained data from the Florida Cancer Data System for women who were diagnosed with breast cancer from 2013 to 2021. A proxy for the effects of structural racism was obtained by using the racial-ethnic-income version of the Index of Concentration at the Extremes (ICE; mediator 1). At the census tract level, ICE scores were calculated, and women were categorized into quintiles ranging from the most- to least-deprived neighborhoods. Health insurance disadvantage was defined as Medicaid coverage, being uninsured, or unknown insurance status (mediator 2). Poisson regression with least squares means was used to assess the adjusted likelihood of living in the most deprived ICE quintile and having insurance disadvantage for Black and White women. Causal mediation analyses using the g-formula were conducted to estimate the total effect (TE), natural direct effect (NDE), and natural indirect effect (NIE) of race on TNBC. Age, region of the state, and marital status were considered as confounders in all models.

Results

Black women were more likely to live in the most disadvantaged neighborhoods (41.6% vs 9.6%) and to experience insurance disadvantage (9.5% vs 6.9%). In mediation analyses, Black women were more likely to be diagnosed with TNBC than White women (18.6% vs 10.2%). On the prevalence difference scale, the following measures were obtained: TE equaled 8.4%, NDE equaled 7.8%, and NIE equaled 0.6%. On the prevalence ratio scale, the following measures were obtained: TE equaled 1.82, NDE equaled 1.76, and NIE equaled 1.04. Nearly 8% of the racial disparity in TNBC is mediated by structural racism and health insurance disadvantage.

Conclusions

Black women with breast cancer have nearly twice the risk of TNBC at diagnosis when compared with White women. Structural racism and insurance were modest contributors to the disparity, underscoring the need for future research to elucidate drivers of TNBC in Black women with breast cancer.