Structural determinants of racial disparities in breast cancer survival in Alabama.

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 1/1/2010 and 12/31/2019. Exposure was self-reported race; mediators were rural-urban status (Rural-Urban Commuting Area codes) and neighborhood deprivation (state-level ADI). Outcome was overall survival from diagnosis to death (any cause) or end of follow-up (12/31/2021). 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 to Black women (n=6,446). After full adjustment with rural-urban and ADI as mediators, there was partial mediation of the race-survival effect (Direct Effect, 95% CI: 1.14, 1.06-1.22; Indirect Effect, 95% CI: 1.10, 1.07-1.12; Proportion Mediated, 95% CI: 0.45, 0.31-0.64). These results mirrored the model with ADI as the only mediator, indicating ADI not rural-urban 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.