Abstract PO1-23-02: Magnetic seeds used for the detection of target lymph nodes after neoadjuvant therapy for early breast cancer – a subgroup analysis of the prospective AXSANA (EUBREAST-03) trial

Abstract

Abstract Background: Surgical strategies for axillary staging in patients with early breast cancer who convert from clinical lymph node positivity (cN+) to a clinically negative lymph node status (ycN0) after neoadjuvant therapy (NAT) vary between breast cancer centers and countries. The international prospective multicenter-cohort study AXSANA (EUBREAST-03) aims to comparatively evaluate long-term outcomes of different surgical staging procedures such as axillary lymph node dissection, sentinel lymph node biopsy (SLNB), target lymph node biopsy (TLNB) and targeted axillary dissection (TAD). A secondary study aim is the comparison of different localization techniques for the target lymph node (TLN), one of which is the use of magnetic seeds. Here we report on the largest so far studied prospective cohort using this technique. Methods: We prospectively examined the retrieval rate of magnetic seeds and the identification rate of a TLN in cN+ patients who underwent NAT and were scheduled for TAD. Magnetic seeds were inserted under ultrasound guidance before the start of NAT. The detection rate of TLN and its associations with residual axillary tumor burden as well as with techniques used for detection of SLN were analyzed. Results: Of the 169 patients with magnetic seed marking of the TLN prior to NAT who were included in the AXSANA study, 135 (79.9%) had undergone final surgery at the time of analysis. 13 patients had 2 magnetic seeds implanted, 122 only 1 seed. In 133 (98.5%) patients the magnetic seeds were successfully identified and removed. No additional procedures or imaging were performed in the two cases with seeds still in situ. In 131 out of 135 patients (97.0%) the TLN was identified and resected, in 4 cases no TLN could be identified although in two of those a dislocated magnetic seed was removed. 85 patients converted from cN+ to ycN0 and a TAD was planned. In 84 of these cases (98.8%) the TLN could be detected during TAD. Eight patients (9.4%) had residual tumor only in the TLN, 15 (17.6%) had residual tumor in TLN and SLN and seven (8.2%) only in the SLN. In 71 (84.2%) cases the TLN was also a SLN. Techniques used for the detection of SLN were Tc99 alone (41.2%), blue dye alone (3.5%), both tracers combined (7.1%), indocyanine green (1.2%) and magnetic tracers (36.5%). Because of the high detection rate of 98.5% for all TLN and 98.8% during TAD a formal analysis of confounding parameters was not performed. Conclusion: To our knowledge this is the largest prospective series of patients using magnetic seeds for the marking of involved lymph nodes prior to NAT. The retrieval rate of the seed and the detection rate for the TLN after NAT is excellent. Magnetic seeds are a reliable tool for the marking of involved lymph nodes before NAT. Citation Format: Hans-Christian Kolberg, Steffi Hartmann, Maggie Banys-Paluchowski, Elmar Stickeler, Jana de Boniface, Oreste Davide Gentilini, Sarah Fröhlich, Marc Thill, Michael P. Lux, Guldeniz Karadeniz Cakmak, Isabel Rubio, Michalis Kontos, Rosa Di Micco, Dawid Murawa, Thorsten Kühn. Magnetic seeds used for the detection of target lymph nodes after neoadjuvant therapy for early breast cancer – a subgroup analysis of the prospective AXSANA (EUBREAST-03) trial [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 PO1-23-02.