Abstract PO4-23-02: Blue Dye-Only for Sentinel Lymph Node Biopsy After Neoadjuvant Chemotherapy in Patients with Initially Node-positive Breast Cancer

Abstract Importance: Randomized trials evaluated the false negative rate (FNR) of sentinel lymph node biopsy (SLNB) in initially node-positive (cN1/2) breast cancer (BC) patients who downstaged after neoadjuvant chemotherapy (NAC): the studies were negative, as they found FNR above 10%. However, the FNR was adequate when the lymph node was marked with a clip before NAC or at least 3 lymph nodes were removed. SLNB using a combination of blue dye and a radiotracer (Technetium-99) was encouraged to facilitate identification and maximize SLNB results in this scenario. However, radiotracer is unavailable in many services around the world, particularly in low- and middle-income countries (LMIC), but the feasibility and the recurrence rates of SNLB with the use of blue dye-only, in previous cN1/2 patients, are unknown. Objective: The aim of this study was to evaluate the feasibility, proportion of patients undergoing SLNB without axillary dissection (AD) and mean number of resected sentinel nodes (SN), and recurrence rates (axillary recurrence AR, ipsilateral breast recurrence IBR, new contralateral primary, disease-free survival DFS and overall survival OS) of SNLB with the use of blue dye-only in initially node-positive BC (cN1/2). Design, Setting, and Participants: From 2013 to 2023, a cohort of patients undergoing NAC was evaluated at a public institution in Brazil (Hospital Geral de Fortaleza - HGF). Radiotracer and clips were not available. Patients with prior cN1/2 were identified and evaluated. AD was not recommended in cases of negative histopathological results for lymph node metastases after SLNB using blue dye-only. Inflammatory, cN0 and cN3 BC patients were excluded. Results: Among 119 cN1/2 BC patients treated with NAC, 100 (84%) cases underwent SLNB with blue dye-only and 70 (59%) had SLNB alone. The median of SN were 3.1 and 55 (78%) cases had 3 or more SN. No events related to blue dye occurred. The median age of these 70 patients was 49 (25-84) years, and most cases were T2 (n=40/57.1%), followed by T3 (n=18/25.7%), T4 (n=6/8.6%) and T1 (n=6/8.6%), while N1 predominated in axillary status (n=64/91.4%). Regarding breast cancer subtype, there were 19 (27.1%) hormone receptor-positive/HER2-negative, 16 (22.9%) hormone receptor-negative/HER2-positive, 21 (30%) hormone receptor-positive/HER2-positive and 14 (20%) triple-negative cases. 55 (79%) patients received regimens containing anthracyclines and taxanes. Anti-HER2 therapy was used in all cases, but pertuzumab associated with trastuzumab were available in only 8 patients (8/37). Breast-conserving surgery was performed in 40 (57%) cases while total mastectomy in 30 (43%). Patients with hormone-positive BC received endocrine therapy. Adjuvant radiotherapy was made in all cases, except one who underwent mastectomy. After 36 months of median follow-up, no axillary recurrences were observed. One patient had a new primary in the contralateral breast. Three patients had distant disease and two died. Conclusions: This cohort found that the use of SLNB with blue dye-only in Initially cN1/2 BC patients who achieved complete response after NAC is feasible, with very low axillary recurrence rates, like previous reports in the literature that used a combination of tracers. These data reinforce the need for further studies in this scenario, as it maintains the possibility of avoiding AD in places with difficult access to oncological treatment, especially in LMIC. Figure 1 - Flowchart cN: Clinical node stage; BC: Breast cancer; NAC: Neoadjuvant chemotherapy; SNLB: Sentinel lymph node biopsy; AD: Axillary dissection; SN: Sentinel node Table 1 - Demographic Characteristics Citation Format: Francisco Pimentel Cavalcante, Felipe Zerwes, Alessandra Souza, Patricia Ziegelmann, Ryane Alcantara, Amanda Cardoso, Andre Mattar, Eduardo Millen, Antonio Frasson. Blue Dye-Only for Sentinel Lymph Node Biopsy After Neoadjuvant Chemotherapy in Patients with Initially Node-positive Breast Cancer abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-23-02.