All-cause mortality by race and socioeconomic status among women treated for breast cancer in metropolitan Detroit

Abstract

Background: Black women with breast cancer in the United States experience significantly higher mortality than White women, despite similar incidence rates. Both biological and socioeconomic factors contribute to this disparity. The Area Deprivation Index (ADI), a composite measure of socioeconomic disadvantage, may provide insight into neighborhood-level influences on survival. We aimed to examine the relative influences of race, ADI, and established clinical risk factors with overall survival among women with breast cancer in Metropolitan Detroit.

Methods: We conducted a retrospective cohort study of 3350 women diagnosed with stage 0-IV breast cancer between 2005 and 2015 at Ascension (now Henry Ford) hospitals in Metropolitan Detroit. Data were extracted from the METRIQ® cancer registry. Variables included race, age, stage, receptor-defined subtype, marital status, insurance, and ADI derived from 9-digit ZIP codes. Kaplan-Meier and Cox proportional hazards models were used to evaluate associations with overall survival.

Results: The cohort was 75.5 % White, 19.6 % Black, and 4.9 % Asian/Other. Mean age at diagnosis was 61.4 years. Survival differed significantly by race, with mean survival of 105.3 months for White versus 96.1 months for Black (p < 0.001). ADI strongly predicted outcomes: women in the most deprived quartile had 26 % lower 10-year survival compared to the least deprived quartile (94.1 vs. 108.2 months, p < 0.001). Survival was also associated with age, hormone receptor positivity, tumor subtype, nodal status, and AJCC pathologic stage (p < 0.001), as well as with HER2 positivity by immunohistochemistry (p < 0.001). Mean survival for cases having luminal A, luminal B, and Her2 enriched histologies were statistically significantly longer at 102.9 ± 1.1 months (95 % CI 100.9-105.0), 103.2 ± 3.4 months (CI 95.6-109.8) and 104.5 ± 4.8 months (CI 95.1-113.9) respectively compared to TNBC at 87.9 ± 3.1 months (CI 81.8-94.0) (p < 0.001). In multivariable Cox regression adjusting for age, stage, and subtype, ADI remained a significant predictor while race dropped from the model.

Conclusions: Breast cancer survival disparities in Metropolitan Detroit are driven predominantly by socioeconomic deprivation as measured by ADI. Although Black women presented at younger ages and with more aggressive subtypes, neighborhood level disadvantage accounted for the largest impact on survival. These findings highlight the need for interventions targeting socioeconomic and environmental determinants of health to reduce racial disparities in breast cancer outcomes.

Keywords: African American Women; Area Deprivation Index (ADI), Socioeconomic Factors; Breast neoplasms; Health disparities; Mortality; Survival Analysis, Detroit (Michigan).