Abstract PS5-04-29: Real-world treatment patterns and outcomes in hormone receptor positive Her2 negative early-stage breast cancer in a private community oncology practice of Brazil

Abstract Purpose: This study aims to assess the disease characteristics, practice patterns and real-world outcomes of patients (pts) with HR positive (+)/HER2 negative (-) early breast cancer (EBC) treated in Brazil's largest network of community oncology practices. Methods: Retrospective study from the Oncoclínicas&CO real-world database from 2016 to 2021. We assessed risk profile distribution (high-risk [HR], intermediate-risk [IR] or low-risk [LR]) as per recent adjuvant trials in EBC, endocrine and chemotherapy (CT) prescriptions and 3-year invasive disease-free survival (iDFS). Results: In total, 1,786 cases were selected for the study. Median age was 57 years, 566 (32%) were premenopausal, 1,179 (66%) were LR, 351 (20%) IR, and 256 (14%) HR. In post-menopausal pts, aromatase inhibitor (AI) was used by 74% with LR, 79% with IR and 83% with HR. In premenopausal pts, ovarian function suppression (OFS) - combined with tamoxifen or AI - was prescribed to 18% LR pts, 15% IR, and 48% HR. CT was offered to 32%, 38%, and 73% of postmenopausal pts in LR, IR, and HR groups. In premenopausal pts, 55%, 57%, and 78% received CT in LR, IR, and HR groups. The 3-year iDFS was 86% (95% CI 84%-89%) in LR population, 87% (82%-91%) in IR, and 72% (95% CI 65%-81%) in HR. Conclusions: In this large real-world cohort of patients treated in a private setting in Brazil, most pts are diagnosed with low-risk EBC. We found that a significant proportion of premenopausal pts with high-risk EBC were not treated with OFS and did not receive CT. Citation Format: A. C. Goncalves, T. Reinert, C. Resende, G. Bretas, M. C. Figueroa, R. Dienstmann. Real-world treatment patterns and outcomes in hormone receptor positive Her2 negative early-stage breast cancer in a private community oncology practice of Brazil [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS5-04-29.