Historical redlining is associated with breast cancer subtype, stage at diagnosis and mortality

Abstract Background: Structurally racist policies have an important impact on health. The etiologic basis of racial disparities in aggressive forms of breast cancer is not well understood. Few studies have investigated the impact of structural racism as a potential driver of etiologic heterogeneity. We sought to estimate the effect of historic redlining on the development of aggressive subtypes and late-stage disease, and examine its role in breast cancer mortality. Methods: Using the Georgia Cancer Registry, we identified 921 non-Hispanic White (NHW) and 878 non-Hispanic Black (NHB) women residing in a Georgia Home Owners' Loan Corporation (HOLC) graded area with a first primary invasive breast cancer diagnosis in 2010–2017. Historic redlining scores for 2010 census tracts were calculated according to the proportion of HOLC grades within the tract. Historic redlining scores were examined continuously and dichotomized at <2.5, which represents areas that were historically considered low for investment risk (Green/“Best” or Blue/“Still Desirable”), vs. ≥2.5, which represents areas that were considered to be high risk (Yellow/“Definitely Declining” or Red/“Hazardous”). We used age-adjusted logistic regression to calculate case-only odds ratios (ORs) and 95% confidence intervals (CIs) associating historically high-risk redlined areas to a diagnosis of Luminal B, HER2, or Triple-Negative breast cancer (TNBC) compared with Luminal A tumors and a diagnosis of Stage II, III, or Stage IV breast cancer compared with Stage I disease. Additionally, we used Cox proportional hazards regression to calculate age-adjusted hazard ratios (HRs) and 95% CIs to associate historically high-risk areas with breast cancer mortality, overall and within each race strata. Results: Overall, 81% of NHB and 19% of NHW women lived in historically redlined census tracts. Women living in redlined areas were diagnosed with more aggressive subtypes (TNBC and HER2) and later stage (Stage III and IV) breast cancers. Compared with Luminal A breast cancer, the ORs for living in historically high-risk vs. low risk investment areas were 2.05 (95%CI=1.44, 2.93) for TNBC and1.49 (95%CI=0.89, 2.48) for HER2 disease. Compared with Stage I breast cancers, the ORs for historically high-risk vs. low risk investment areas were 1.85(95%CI=1.30, 2.63) for Stage III and 2.00 (95%CI=1.32, 3.02) for Stage IV breast cancer. Residing in historically high-risk census tracts was associated with a 1.68-fold increase in breast cancer mortality (95% CI=1.23, 2.30), after adjusting for age. The association was most pronounced among NHW women living in redlined census tracts (HR=1.36; 95%CI=0.99, 1.87); a near-null association was observed among NHB women (HR=0.97; 95% CI=0.78, 1.20). Conclusions: Historic redlining scores were associated with the diagnosis of more aggressive forms of breast cancer and breast cancer mortality. Historic place-based measures of structural racist policies have modern-day implications on health outcomes and may underpin reported disparities in aggressive or advanced tumor types. Citation Format: Jasmine M. Miller-Kleinhenz, Maret L. Maliniak, Micah J. Streiff, Leah Moubadder, Lauren E. Barber, Rebecca Nash, Lindsay J. Collin, Jeffrey M. Switchenko, Kevin C. Ward, Lauren E. McCullough. Historical redlining is associated with breast cancer subtype, stage at diagnosis and mortality [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr C093.