Impact of socioeconomic status and rurality on cancer-specific survival among women with de novo metastatic breast cancer by race/ethnicity

PURPOSE: There are approximately 150,000 women living with metastatic breast cancer (mBC) in the United States. Disparities in de novo mBC incidence and mortality exist across race/ethnicity, socioeconomic status (SES), and rurality. However, how SES and rurality independently impact mBC outcomes across different racial/ethnic groups is not fully understood. The purpose of this study was to determine the impact of SES and rurality on cancer-specific mortality among women with mBC by race/ethnicity. METHODS: We conducted a large, population-based retrospective cohort study in women aged 18 + years diagnosed with de novo mBC using the Surveillance, Epidemiology and End Results Census Tract-level SES and Rurality Database (2000–2015). Associations between SES/rurality and cancer-specific mortality were determined using Fine and Gray regression models. Subdistribution hazard ratios (SHR) and 95% confidence intervals (CI) by race/ethnicity and hormone receptor (HR) status were calculated. RESULTS: A cohort of 33,976 women were included with the majority being White (67%), 17% Black, 0.4% American Indian/Alaskan Native, 6% Asian/Pacific Islander, and 10% Latina/Hispanic. We observed the greatest increased risk of BC mortality among Black women with HR-negative mBC residing in neighborhoods with lower SES (lowest versus highest quintile: SHR 1.38, 95% CI 1.00–1.90) and in rural areas compared to urban areas (SHR 1.27, 95% CI 1.01–1.59). CONCLUSION: Overall, BC-specific survival among women with de novo mBC differs by race/ethnicity, with the greatest adverse impacts of SES and rurality affecting Black women with HR-negative disease.