Clinical Outcomes of Adjuvant Hormone Therapy in a Cohort of Patients With Infiltrating Non-metastatic Breast Cancer in a Latin American Cancer Center

Introduction: Breast cancer (BC) is the most commonly diagnosed cancer in women. This study evaluated the clinical outcomes and prognostic factors associated with disease-free survival (DFS) and overall survival (OS) in a cohort of patients diagnosed with hormone receptor-positive non-metastatic BC managed with adjuvant hormone therapy. Methods: An observational, analytical, historical cohort study was conducted. DFS and OS rates were estimated, Kaplan-Meier survival functions were calculated, and Cox models were developed to assess the association between time to event (all-cause mortality or relapse) and hormone therapy exposure with a set of established variables. Results: Inclusion criteria were met by 685 patients; the mean age at diagnosis was 58 years (SD=11.9 years). The most commonly used drug was tamoxifen for five years in 241 (35.7%) patients; 470 (69.6%) patients received initial therapy, 112 (16.5%) underwent switch therapy, and 93 (13.8%) had extended therapy. The factors associated with better rates of DFS and OS were early clinical stage (p=0.00), luminal A and luminal B Her2-positive biological subtypes (p=0.00), and adherence to adjuvant hormone therapy (p=0.001). Mortality rate was 0.77 deaths per 100 patients/year (95% CI, 0.51-1.2). Conclusion: This cohort demonstrated that adjuvant hormone therapy improves DFS and OS rates in locally advanced tumors. The main factor for reducing disease progression in this cohort was adequate adherence to treatment.