Abstract PO3-22-09: Implementation of nanoparticle-assisted axillary staging: reduced axillary intervention for patients with node-positive breast cancer following neoadjuvant therapy

Abstract Background: Nanoparticle-assisted axillary staging (NAAS), which combines carbon nanoparticles with standard dual-tracer (radioisotope and blue dye) sentinel lymph node biopsy (SLNB), has shown excellent results in patients undergoing neoadjuvant therapy (NAC) for pre-NAC node-positive breast cancer. This pilot study aimed to explore the possible expansion of indications (pre-NAC cN2, and cN3 stages; ycN+ stage) for NAAS, which was the first attempt till now for patients undergoing NAC, and to select specific post-NAC individuals who might be exempt from axillary lymph node dissection (ALND), especially those with relatively low tumor burdens, such as ITCs and micrometastases. Method: The medical records of all consecutive patients with breast cancer were prospectively collected from the Breast Center, West China Hospital. Patients with invasive, pre-NAC node-positive breast cancer who underwent NAAS followed by ALND between April 2021 and February 2023 were included. The detection rate (DR), average number of sentinel or NAAS nodes, false negative rate (FNR), negative predictive value (NPV), and NAAS accuracy were assessed. Subgroup analyses according to different pre- and post-NAC cN stages, especially the pre-NAC cN2-3 stages and the post-NAC cN+ stages, which were not the focus of previous studies, were conducted using crosstabs. To screen possible patients who might exempt ALND, we focus on relationships between the status of axillary lymph nodes and the number or tumor burden of NAAS nodes. Results: A total of 241 eligible patients were included in the study. There were 153 (63.49%), 40 (16.60%), and 48 (19.92%) patients in pre-NAC cN1, cN2, and cN3 stages, respectively. The post-NAC stages of patients were not restricted, 38.17% (92/241) of them converted to ycN0 stages, while 61.83% (149/241) were still in ycN+ stages. A total of 232 (96.27%) eligible patients successfully underwent NAAS; the DR, NPV, accuracy, and FNR of NAAS were 96.27%, 95.97%, 97.84%, and 4.42%, respectively. Additionally, NAAS showed accuracies of 97.30% and 93.02% and FNRs of 7.14% and 9.09% in patients with pre-NAC cN2 and cN3 breast cancers, respectively. There was no statistical difference among the FNRs of NAAS in the pre-NAC cN1, cN2, and cN3 stages (p=0.134). Moreover, NAAS yielded FNRs of 0.00% in the ycN0 population and 6.02% in the ycN+ population, respectively (p=0.323). Accuracies reached 100.00% and 96.48% in ycN0 and ycN+ patients, respectively (p=0.159). Notably, patients with one NAAS node with ITC or micrometastasis in the entire population showed no further positive disease at ALND. Conclusion: NAAS showed excellent and stable performance with a low FNR and high accuracy, indicating valuable application prospects in patients with breast cancer who received NAC. Patients with pre-NAC cN2-3 stages also have a chance to undergo NAAS, and the application of NAAS appears to be feasible regardless of the ycN stage. Especially for ycN0 population, there is no chance for NAAS to miss positive axillary lymph nodes. In addition, patients who had one NAAS node with ITC or micrometastasis might avoid ALND. Diagnostic performance of nanoparticle-assisted axillary staging in pre-neoadjuvant chemotherapy cN1, cN2 and cN3 patients Diagnostic performance of nanoparticle-assisted axillary staging in ycN0 and ycN+ patients Additional axillary disease at axillary lymph node dissection in patients with positive NAAS nodes after neoadjuvant chemotherapy XX- XX XX- XX XX- XX Citation Format: Ruixian Chen, Tao He, Jiqiao Yang, Shan Lu, Yunhao Wu, Chihua Wu, Ruoning Yang, Weijing Liu, Ya Huang, Xiangyue Meng, Xin Zhao, Qintong Li, Xin Sun, Jing Jing, Jie Chen. Implementation of nanoparticle-assisted axillary staging: reduced axillary intervention for patients with node-positive breast cancer following neoadjuvant therapy [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 PO3-22-09.