Abstract
BACKGROUND: Despite improvements in breast cancer survival, Black versus White women remain at higher risk of death. Exploring reasons behind this disparity is necessary to facilitate interventions. This study evaluated rural-urban residence and/or area deprivation index (ADI) as mediators of the association between race and survival in adults with breast cancer in Alabama. METHODS: This retrospective, population-based cohort included 25,195 adult Black or White women with incident breast cancer in Alabama between January 1, 2010, and December 31, 2019. Exposure was self-reported race; mediators were rural-urban status (Rural-Urban Commuting Area codes) and neighborhood deprivation (state-level ADI). The outcome was overall survival from diagnosis to death (any cause) or end of follow-up (December 31, 2021). RESULTS: White women (n = 18,749) were older at diagnosis (62.4 vs. 58.7; P < 0.001), had fewer deaths (21.6% vs. 25.8%; P < 0.001), longer follow-up (70.2 vs. 66.7 months; P < 0.001), lower ADI (4.1 vs. 6.3; P < 0.001), and more rural dwellers (23.2% vs. 18.3%; P < 0.001) compared with Black women (n = 6,446). After full adjustment with rural-urban status and ADI as mediators, there was partial mediation of the race-survival effect [direct effect: hazard ratio = 1.14; 95% confidence interval (CI), 1.06-1.22; indirect effect: hazard ratio = 1.10; 95% CI, 1.07-1.12; and proportion mediated: hazard ratio = 0.45; 95% CI, 0.31-0.64]. These results mirrored the model with ADI as the only mediator, indicating that ADI and not rural-urban status drove the indirect effect. CONCLUSIONS: Among Black and White Alabamian women with breast cancer, 45% of the survival disparity is mediated by differences in neighborhood deprivation. IMPACT: Almost half of the Black-White difference in breast cancer mortality would be eliminated if differences in neighborhood deprivation were improved. See related commentary by Pinheiro and Reeder-Hayes, p. 1683.