Abstract PS5-10-19: Breast cancer in young women at a private center in Chile

Abstract Introduction Breast cancer is the most frequently diagnosed cancer worldwide and the second leading cause of cancer-related death. While it predominantly affects women over 40, 5-7% of cases occur in those under 40 in developed countries. Despite its lower incidence in younger women, it remains the leading cause of cancer death in this group, underscoring the need to better understand its biology, treatment, and outcomes in younger patients. Objectives This study aims to analyze the clinical and pathological characteristics of breast cancer cases treated at Clínica Alemana in Santiago, Chile, over the past decade, and to compare them with global data. Specific objectives include evaluating tumor biology, reason for consultation, type of surgery, recurrence patterns, and mortality. Methods and materials Retrospective descriptive study of clinical presentation, tumor features, treatments, and fertility in 200 women aged ≤40 with breast cancer over 10 years at Clínica Alemana, Santiago, Chile. Results Among the total cohort, 17.7% underwent fertility preservation prior to treatment. Adjuvant radiotherapy was administered to 58.9%, chemotherapy (neoadjuvant/adjuvant) to 40.6%, and hormone therapy to 79.1%—of whom 96.7% received Tamoxifen and 3.3% aromatase inhibitors. Recurrence occurred in 6.8%, with 38.5% local, 7.7% regional, and 53.8% distant metastases. At follow-up, 97.4% were alive; 5 deaths were due to metastatic disease. Discussion The distribution of tumor stages in our cohort is consistent with patterns observed in high-income countries, with 69% of cases diagnosed at stage I or II and 3% at the metastatic stage. Although breast cancer in women < 40 is generally associated with more aggressive subtypes, our cohort exhibited lower rates of HER2 (+) (18%) and triple-negative (8%) tumors compared to reported averages. Additionally, the 5-year cumulative incidence of distant metastases was notably lower in our population (4.7% vs. 18-24%), and the overall 5-year survival rate was higher (97.4% vs. 89-93%). Citation Format: M. E. Gonzalez, J. Camacho, C. Barriga, M. Bravo, P. Pincheira, M. Gallegos. Breast cancer in young women at a private center in Chile [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 PS5-10-19