Abstract
This study analyzed breast cancer patients treated with trastuzumab in Brazil's unified health system (SUS) from 2008 to 2015. A non-concurrent cohort study using SUS data applied propensity score matching to reduce bias between trastuzumab and non-trastuzumab groups. Survival probabilities were estimated via Kaplan-Meier, with subgroup analysis using the log-rank test. Hazard ratios (HR) were calculated using Cox proportional hazards models. Among 20,852 patients, the overall survival rate was 92%, with 94% in the trastuzumab group and 90% in the non-trastuzumab group. Younger, black patients and those in the North region had poorer survival. Advanced disease stages and palliative treatments were linked to higher mortality, while adjuvant therapy and radiotherapy were protective. During follow-up, 8.1% of patients died, with better outcomes observed in the trastuzumab group (p < 0.0001). Late initiation of trastuzumab (after 16 months) improved survival, especially in early stages (I and II). Invasive tumors and stage IV disease were associated with worse prognoses. The study demonstrates trastuzumab's effectiveness in SUS, underscores survival disparities related to sociodemographic factors, and emphasizes the need for early detection, equitable access, and optimized treatment timelines to improve outcomes in public healthcare.