1043 – Neoadjuvant endocrine therapy in breast cancer: a single-institution epidemiological and clinicopathological analysis from southern Brazil

Abstract

Introduction: Breast cancer accounts for approximately 11.6% of all oncologic diagnoses, with hormone receptor-positive (HR+) and HER2 negative (HER2-) tumors representing a significant proportion of cases. In this context, neoadjuvant
endocrine therapy has emerged as a therapeutic alternative, with potential benefits in tumor downstaging and increased
rates of breast-conserving surgery. The aim of this study was to describe the epidemiological and clinicopathological profile of patients with HR+/HER2− breast cancer undergoing neoadjuvant endocrine therapy in a public healthcare setting,
as well as to analyze treatment response rates.
Methods: An observational, analytical, retrospective study was conducted including patients treated between January
2019 and October 2025 who underwent surgery after neoadjuvant therapy. Clinical, pathological, and outcome variables
were assessed.
Results: The cohort included 25 patients, with a mean age of 73.7 years and multiple comorbidities. There was a predominance of T2 tumors (64%), N0 disease (60%), and histological grade 2 (68%), with high expression of hormone receptors
(mean ER 92.6% and median PR 60%) and a median Ki-67 of 15%. Anastrozole was used in 96% of cases, with a median
treatment duration of 8 months. The breast-conserving surgery rate was 64%, with a reduction in mean tumor size from
3.2 cm to 2.7 cm. The PEPI score was calculated in eligible patients, with scores greater than 4 in 68% of cases, and 12%
presenting high residual axillary burden (ypN3a). At a median follow-up of 27 months, no locoregional recurrences were
observed.
Conclusion: In a real-world setting, neoadjuvant endocrine therapy proved to be safe and feasible for the treatment of
HR+/HER2− breast cancer, particularly regarding tumor control and treatment timing. Proper patient selection may optimize surgical outcomes and support individualized treatment strategies.
Ethics: Research Ethics Committee Approval (CAAE 92207025.0.0000.5335)