Radar reflectors for marking of target lymph nodes in patients receiving neoadjuvant chemotherapy for breast cancer: A subgroup analysis of the prospective AXSANA (EUBREAST-03) trial.

579 Background: Surgical staging procedures of the axilla in breast cancer patients converting from a clinically positive (cN+) to a clinically negative (ycN0) lymph node status during neoadjuvant chemotherapy (NACT) vary across countries. The international prospective AXSANA study aims at comparatively evaluating outcomes of different procedures such as axillary lymph node dissection (ALND), sentinel lymph node biopsy (SLNB), target lymph node biopsy (TLNB), and targeted axillary dissection (TAD). In this subgroup analysis, we report on the largest prospective cohort of patients receiving a radar reflector for TLN marking prior to NACT. Methods: AXSANA is a cohort study including cN+ → ycN0 patients treated with NACT. Eligible patients initially have cT1-4c tumors. In the present analysis, only patients with a TLN marked by a radar reflector were included. We examined the retrieval rate of radar reflectors and the identification rate of the TLN (defined as unequivocal removal of the lymph node, i.e., lymphatic tissue in the TLN specimen and/or pathological confirmation of changes typical for metastatic nodes responding to treatment). Results: A TLN was marked using a radar reflector in 123 patients prior to NACT. Most patients (n = 64, 52.0%) had one suspicious node at time of diagnosis, followed by two (n = 32, 26.0%), three (n = 22, 17.9%) or ≥ 4 suspicious nodes (n = 5, 4.1%). In 5 out of 22 (23%) patients who had a MRI during NACT, artifacts were visible and limited tumor assessment in one patient. Out of the 123 patients with radar reflector marked TLN, 93 (75.6%) had undergone final surgery at the time of analysis, 75 of whom (80.6%) had converted to ycN0. Most patients had undergone a TAD (n = 86, 92.5%), followed by ALND in 3.2% of cases (n = 3) and TLNB (n = 1, 1.1%). 3 patients received other procedures, such as combined TLNB / ALND. In 83 out of 85 patients (98%) with available postoperative histopathology, the TLN was unequivocally identified and removed. In one patient, no lymphatic tissue was identifiable in the tissue specimen containing radar reflector, so it remains unclear whether the TLN was excised, or the reflector had dislocated. In another patient, the radar reflector was not identified intraoperatively but postoperative computed tomography confirmed removal. Thus, no radar reflectors were left behind. Conclusions: To the best of our knowledge, this is the largest prospective series of patients receiving a radar reflector for the marking of TLN prior to NACT for breast cancer, demonstrating very high detection and removal rates of TLN and marker. Radar reflectors are a reliable tool for marking of TLNs in the neoadjuvant setting. Clinical trial information: NCT04373655 .