Abstract PS3-10-05: Indications and Outcomes of Anthracycline-Based Regimens for Early-Stage Grade 3 Hormone Receptor-Positive Breast Cancer in a Real-World Scenario

Abstract Background: In hormone receptor-positive (HR+) breast cancer, anthracycline-free chemotherapy regimens—most commonly the TC regimen (docetaxel and cyclophosphamide)—have been widely adopted, particularly for early-stage, node-negative disease. However, certain HR+ patients, such as those with higher genomic risk, may still benefit from anthracycline-based chemotherapy. This study aimed to evaluate real-world treatment practices in an intermediate- to high-risk population, specifically patients with grade 3 tumors. Methods: We retrospectively reviewed records of patients with early-stage HR+ grade 3 breast cancer treated between 2018 and 2025 across a Brazilian cancer network. Eligible patients had received systemic therapy (neoadjuvant or adjuvant) for early-stage disease. Patients were categorized by chemotherapy regimen into anthracycline-based and anthracycline-free groups. We used logistic regression to assess the odds of receiving an anthracycline-based regimen based on clinical and demographic features. Event-free survival (EFS) was estimated using the Kaplan-Meier method, and factors associated with EFS were evaluated using Cox regression. Results: A total of 215 patients were included; 92 (42.8%) received anthracycline-based and 123 (57.2%) received anthracycline-free chemotherapy. Patients were more likely to receive anthracycline-based regimens if they were younger, premenopausal, had higher T or N stage, or had a Ki-67 index ≥ 20%. The distribution of these characteristics and their associated odds ratios (ORs) are shown in the Table (reference categories: age ≥ 50 years, postmenopausal, T1, N0, Ki-67 < 20%). Nearly half of the anthracycline group (46.7%) received the regimen as neoadjuvant therapy, whereas almost all patients in the anthracycline-free group (97.6%) were treated in the adjuvant setting. With a median follow-up of 23 months, 15 patients experienced disease recurrence or death. The 2-year EFS was 97.1% in the anthracycline group and 97.4% in the anthracycline-free group. In multivariable Cox regression adjusting for age and stage, there was no significant difference in EFS between the groups (HR 1.51, 95% CI 0.44-5.16; P = 0.508). Discussion: In this real-world cohort, anthracycline-based chemotherapy was more frequently used in patients with higher-risk features, including younger age and more advanced stage. No difference in short-term EFS was observed between patients who received anthracycline and those who did not, although the analysis is limited by the small sample size, low event rate, and relatively short follow-up. We plan to expand the cohort and extend follow-up to further investigate this question. Citation Format: L. G. Torres, J. Bines, L. Testa, D. Negrini, V. Petry, A. C. Baptista, C. R. Victor, W. A. Lima, R. Naves, C. A. Cavalcanti, L. Holland, P. H. Divino, M. Nogueira, J. d. Bessa, R. Colombo Bonadio. Indications and Outcomes of Anthracycline-Based Regimens for Early-Stage Grade 3 Hormone Receptor-Positive Breast Cancer in a Real-World Scenario [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 PS3-10-05.