Education, income, treatment, and survival: A retrospective cohort study of patients with breast cancer in Sao Paulo, Brazil.

Abstract

e13620 Background: Socioeconomic factors influence breast cancer stage at diagnosis, access to treatment, and survival, yet their impact in middle-income settings remains underexplored. This study examines the effect of education attainment and GDP on treatment utilization and survival outcomes among patients diagnosed with breast cancer in São Paulo, Brazil. Methods: We conducted a retrospective cohort study including incident cases of invasive breast cancer recorded in the São Paulo FOSP registry between 2000–2019. The primary outcomes were overall survival and differences between expected and observed treatment utilization. The primary explanatory variables of interest were educational attainment and GDP. Overall and cancer-specific survival were estimated using Kaplan–Meier methods and multivariable Cox regression. Using previously published health-services modelling frameworks, we compared expected versus observed utilization of chemotherapy, surgery, radiotherapy, and endocrine therapy, stratified by stage. Guideline-concordant care was evaluated among patients with stage III disease. Results: The cohort included 125,005 patients. Educational attainment showed a clear stepwise association with survival: median overall survival ranged from 6.2 years among unlettered patients to 20.6 years among those with a university education. In multivariable analysis, university-educated patients had a 50% lower risk of death compared with unlettered patients (HR 0.50, p < 0.001). GDP was associated with survival but demonstrated weaker and less consistent gradients. Educational attainment strongly influenced treatment patterns: chemotherapy utilization exceeded modelled expectations in stage II but fell below expected levels in stages III–IV, with the largest shortfalls among patients with lower education. Radiotherapy and endocrine therapy utilization were below expected across all groups. Among patients with stage III disease, receipt of all guideline-concordant care was associated with markedly improved survival (median 9.4 vs 3.6 years; HR 0.44, p < 0.001). University educated patients with stage III breast cancer had the highest proportion that received all guideline concordant care (60.5%) while among unlettered patients, only 36.3% received all guideline-concordant care. Conclusions: Educational attainment emerged as a major determinant of treatment utilization and survival. Lower education was associated with later stage at diagnosis, lower receipt of chemotherapy, radiotherapy, and endocrine therapy, reduced guideline-concordant care, and substantially poorer outcomes. These findings highlight the need for policies that address social and structural barriers to timely, high-quality cancer care and demonstrate the utility of modelling approaches for identifying and quantifying inequities in treatment delivery.