The effect of time on associations between historical redlining and breast cancer survival

Abstract Background Historical redlining, a 1930s residential segregation policy, has been associated with shorter breast cancer survival. It is unknown whether this disparity has changed over time, given the time since redlining increases and subsequent breast cancer advances have occurred. This study evaluated whether associations between historical redlining and all‐cause survival of breast cancer have changed from 1995 to 2019. Methods This New York State Cancer Registry–based cohort included 135,827 patients with breast cancer who were diagnosed between 1995 and 2019 and resided in a historically graded census tract at diagnosis. Cases were assigned a historical redlining grade (range, A–D) and divided into 5‐year diagnostic time periods. Cox models estimated associations with survival. Multiplicative interaction between redlining grade and period tested temporal effects. Models were stratified by stage, hormone receptor status, and race/ethnicity. Results A significant time interaction with historical redlining for survival was found ( p < .0001). Survival disparities for D grade versus A grade were largest in 1995–1999 (hazard ratio HR, 1.75; 95% CI, 1.55–1.98) and lowest in 2005–2009 (HR, 1.48; 95% CI, 1.32–1.66). Redlining associations for local and regional tumors were largest in 1995–1999 and attenuated over time. Redlining was generally not associated with survival among distant tumors. D‐grade versus A‐grade survival disparities grew over time among patients with hormone receptor–positive tumors. Significant temporal effects were detected among all race/ethnicity groups. Conclusions Associations between historical redlining and breast cancer survival have changed over time, with disparities generally narrowing. Results stratified by stage and hormone receptor status suggest that such disparities reflect differential access to advances in breast cancer treatment across time.