Social inequalities in survival among women with breast cancer in southeastern Brazil: a retrospective cohort study.

Background: Breast cancer (BC) remains the most common malignancy among women worldwide and a leading cause of cancer-related death, particularly in low- and middle-income countries. Social inequalities are known to influence access to diagnosis, treatment, and survival outcomes. However, evidence on these disparities in middle-income settings, such as Brazil, remains limited. Here, we investigated the association between sociodemographic factors and survival among women diagnosed with BC treated at all hospitals that comprise the Oncology Care Network of a state in southeastern Brazil. Methods: We conducted a hospital-based retrospective cohort study using data from the Hospital Cancer Registries and the Mortality Information System of Espírito Santo, Brazil. The cohort included 12,096 women diagnosed with BC. Cases were categorized as death from BC, death from other causes, or survival at 5 years. Five-year survival was estimated using the Kaplan-Meier method and compared using the log-rank test. A Cox proportional hazards model for cause-specific mortality was applied for multivariate analysis. Results: Among the cohort, 8,184 (67.66%) women survived until the end of follow-up, 2,947 (24.28%) died from BC, and 975 (8.06%) died from other causes. The overall cause-specific survival at 5 years was 82%. Multivariate analysis revealed that race was an independent risk factor for BC-specific mortality: Black women had a 60% higher risk of death compared with White women [hazard ratio (HR) =1.601; 95% confidence interval (CI): 1.303-1.967; P<0.001]. Similarly, marital status was associated with survival, as single women had a 31% higher risk of BC-specific death compared with married women (HR =1.314; 95% CI: 1.188-1.454; P<0.001). Conclusions: Significant social inequalities in 5-year BC survival were observed, primarily influenced by age at diagnosis, race/skin color, marital status, and educational level. These findings highlight the urgent need for public health strategies to reduce disparities and improve equity in BC care in Brazil.