Abstract PS5-06-17: Sentinel lymph node biopsy after neoadjuvant chemotherapy in patients with breast cancer using blue dye alone: Results from a multicenter study in Public Hospitals in Brazil

Abstract Introduction: In recent decades, breast cancer surgery has evolved from radical procedures to more conservative approaches, with emphasis on sentinel lymph node biopsy (SLNB), which reduces morbidity without compromising oncologic control. The introduction of neoadjuvant chemotherapy (NAC) has expanded the use of SLNB, even in patients with initially clinically positive axilla (cN1/N2) who converted to clinically negative status after treatment. However, the safety of this technique in cN1/N2 scenarios remains debated, especially given the lack of resources such as dual tracer techniques (using both blue dye and technetium for sentinel node identification) and lymph node clip placement in public health systems. Methods: This multicenter retrospective study analyzed 369 breast cancer patients treated with NAC between 2017 and 2021 at three public hospitals in Brazil. Patients were grouped according to their pre NAC axillary status and the type of axillary surgery performed, either SLNB or axillary lymph node dissection (ALND). All patients had clinically negative axilla following NAC. Objective: The primary objective was to evaluate axillary recurrence in patients who were initially cN1/N2 and converted to cN0. Results: Among patients who underwent SLNB using blue dye alone as the sole mapping method, the axillary recurrence rate was 2.4% in the group initially with clinically negative axilla (cN0) and 2.6% in the initially cN1/N2 group, with no statistical difference. Overall survival (OS) was also similar, at 94.1% in the cN0 group and 89.7% in the cN1/N2 group, without statistical significance (p=0.255), as were the other survival outcomes analyzed. When comparing initially cN1/N2 patients who underwent SLNB or ALND, similar axillary recurrence rates were observed: 2.6% in the SLNB group and 2.3% in the ALND group. OS of 89.7% and 87.8%, respectively, also showing no statistically significant difference. Furthermore, when all 163 patients who underwent SLNB were grouped regardless of initial axillary status and compared to the 206 patients who underwent ALND, the axillary recurrence rates remained comparable: 2.5% in the SLNB group and 1.9% in the ALND group. Other outcomes, including local and locoregional recurrence, disease-free survival, distant disease-free survival and overall survival, also showed similar results between groups. Conclusion: SLNB with blue dye alone, even without complementary techniques, demonstrated acceptable oncologic safety in patients who converted to cN0 after NAC. These findings are especially relevant in resource-limited settings and support the use of less invasive strategies to reduce complications without compromising therapeutic effectiveness. Further studies are needed to validate these results. Keywords: Breast cancer; Sentinel lymph node biopsy; Neoadjuvant chemotherapy; Axillary lymph node dissection; Public Health System. Citation Format: C. Lopes, R. S. Machado, S. Trota, T. Orge, L. Oliveira, D. Torres, F. Bacellar, S. Paiva, L. Piana, J. Bines. Sentinel lymph node biopsy after neoadjuvant chemotherapy in patients with breast cancer using blue dye alone: Results from a multicenter study in Public Hospitals in 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 PS5-06-17.