Abstract PS2-05-13: Evaluation of Axillary Treatment in Patients with Early Breast Cancer According to Study Z0011 in a Public Tertiary Hospital in the Federal District, Brazil

Abstract Introduction: The radical mastectomy technique described by Halsted in 1894 was based on the concept that more extensive surgical resection increased the likelihood of patient cure. Over more than 120 years, medical knowledge about breast cancer has expanded, enabling less mutilating treatments with equal or better survival rates, especially following studies on tumor biology. Axillary surgical treatment has been a significant milestone, changing medical management and reducing the rates of axillary lymph node dissection after the publication of the American College of Surgeons Oncology Group Z0011 clinical trial, that demonstrated that patients with initial cT1-T2 tumors without palpable axillary adenopathy, undergoing breast-conserving surgery, systemic adjuvant treatment, and radiotherapy, maintained overall survival and distant recurrence-free survival rates, even with 1 or 2 metastatic axillary lymph nodes, compared to those who underwent axillary dissection. Objectives: To evaluate the applicability of the Z0011 protocol in the axillary treatment of early invasive breast cancer and its impact on reducing axillary lymph node dissection by omitting this surgical treatment. Method: This is an observational, descriptive, retrospective study based on data collected from the medical records of patients who underwent surgical treatment at a public hospital, Hospital de Base, in the Federal District, Brazil. Results: A total of 119 patients from the mastology service at Hospital de Base met the Z0011 eligibility criteria. Nine patients were excluded due to failure in patent blue migration, resulting in 110 patients included in the study. The average age of patients was 58 years (ranging from 35 to 83 years). The predominant immunohistochemical profile was luminal B (55%), followed by luminal A (30%), HER2 positive (9%), and triple-negative (6%). Among the HER2 positive patients, 80% also had positive hormone receptors (HR), while 20% were HR negative. Among the 110 patients, 27% had sentinel lymph node (SLN) metastasis. Specifically, 19% had metastasis in 1 SLN, 3% had metastasis in 2 SLNs, and 5% had metastasis in 3 or more SLNs. Consequently, 83% of patients with 1 or 2 metastatic SLNs did not undergo lymphadenectomy, representing a significant omission of axillary surgical treatment. Conclusion: The successful replication of the Z0011 protocol in our study demonstrates the significant potential for reducing axillary lymphadenectomy in patients treated at our hospital, with an observed 83% reduction in axillary dissection among patients with axillary lymph node metastasis. These findings are particularly important as they underscore the feasibility of implementing the Z0011 protocol in a public hospital setting, providing evidence that even in resource-constrained environments, it is possible to achieve substantial improvements in patient care. Keywords: Breast cancer; Sentinel lymph node; Axillary metastases; Lymphadenectomy. Citation Format: T. K. Vivan, M. Passos, V. X. Santana, F. C. Salum, C. Fuschino, A. F. Esterl, R. Pepe. Evaluation of Axillary Treatment in Patients with Early Breast Cancer According to Study Z0011 in a Public Tertiary Hospital in the Federal District, 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 PS2-05-13.