Breast Cancer–Specific Survival and Prognostic Factors in a Statewide Oncology Network in Brazil: A Registry-Linked Retrospective Cohort Study

Abstract

Background: Breast cancer survival varies widely across middle-income settings and may be influenced by clinical stage at diagnosis and access pathways within oncology care networks. In Brazil, evidence from statewide cohorts using linked registry and mortality data remains limited. Aim: To investigate the association between clinical factors and breast cancer–specific survival among women treated in all hospitals comprising the Oncology Care Network of a state in Southeastern Brazil. Methods and Results: A retrospective cohort study was conducted using data from the Hospital Cancer Registry linked to the state Mortality Information System. Women aged ≥ 18 years diagnosed with primary breast cancer (ICD-10: C50.x) between 2000 and 2016 were included and followed until December 31, 2021. Five-year breast cancer–specific survival was estimated using the Kaplan–Meier method, and factors associated with mortality were assessed using cause-specific Cox proportional hazards models with complete-case analysis. A total of 12,096 women were included, of whom 7,191 had complete data for multivariable analysis. The mean age at diagnosis was 54.7 years. Five-year breast cancer–specific survival ranged from 97% (95% CI: 96−97%) in stage I to 32% (95% CI: 31−37%) in stage IV. Women referred from the private healthcare system had a significantly lower risk of breast cancer mortality than those referred from the public system (HR: 0.83; 95% CI: 0.75−0.93; p = 0.001). Advanced clinical stage remained the strongest predictor of mortality, and the presence of distant metastasis at diagnosis increased the risk of breast cancer death by 49% (HR: 1.49; 95% CI: 1.14−1.94; p = 0.003). Conclusion: Breast cancer–specific survival in Espírito Santo is strongly determined by stage at diagnosis and by differential access pathways within the oncology care network. Strengthening early diagnostic strategies, improving referral coordination, and ensuring equitable access to timely treatment are essential to reduce survival disparities in this setting.