Abstract PO4-23-01: Imaging tailored axillary approach combined with radiotherapy eliminates axillary lymph node dissection in low-volume axillary disease after neoadjuvant chemotherapy

Abstract ABSTRACT Background Individualized treatment strategies are highlighted for breast cancer patients in the last decades. Therefore aggressive surgical approaches have begun to evolve towards minimally invasive tailored interventions. SLNB is widely used in patients who received neoadjuvant treatment (NAC) and axillary lymph node dissection (ALND) is recommended for patients with axillary residual disease after NAC. In our study, we investigated regional recurrence rates in patients with limited axillary residual disease after NAC who underwent imaging-guided (MR+USG) axillary surgery plus radiotherapy (RT) instead of ALND. Materials and Methods 139 patients whose clinical stages were T1-3 and N1 at the time of diagnosis, who had a clinically good or complete axillary response after neoadjuvant therapy, and who had axillary residue (≤3 pathological lymph nodes) with favorable response to NAC (50% fibrotic changes) in the final pathological examination were included in the study. The tumor stage and the number of pathological lymph nodes were assessed by USG, MMG, MR, and PET-CT examination (The minimum number of lymph nodes to be removed was determined according to imaging findings). All patients underwent imaging-guided SLNB (blue dye) and imaging-guided palpable lymph node excision. The patients were re-evaluated with their final pathology results in the multidisciplinary councils for suitable further treatments, ALND or RT. Peripheral lymphatic radiotherapy was applied to patients whose radiology and pathology results were compatible and no further surgery was done. The patients whose radiologically detected number of positive nodes was inconsistent with the number of metastases in pathology examination and who were presumed to have the gross residual disease underwent ALND. These patients were excluded from the study. Results The median age was 47 years. The median number of lymph nodes excised was 4. The total number of excised lymph nodes was between 1-3 in 64 (46%) patients and between 4-6 in 62 (45%) patients. 13 (9%) patients had ≥7 lymph nodes. 1 metastatic lymph node was found in all patients with 1 positive lymph node according to imaging findings. Of 41 patients with 2 radiologically positive lymph nodes, 1 metastatic lymph node was found in 17 (41%) patients, 2 metastatic lymph nodes in 22 (53%), and 3 metastatic lymph nodes in 2 (5%) patients respectively. Radiology reported 3 positive lymph nodes in 22 patients, of which 1 metastatic lymph node was found in 8 (36%), 2 metastatic lymph nodes in 10 (45%), and 3 metastatic lymph nodes in 4 (18%). The median follow-up period was 44 months. One patient had breast recurrence at the 31st month and one patient had lymphatic recurrence in the supraclavicular area at the 39th month. Systemic recurrence was noted in 6 (4.3%) patients. No axillary recurrence occurred during the follow-up period. Conclusions Patients with pathological-suspicious ≤ 3 lymph nodes shown by imaging (USG, MR, and PET-CT) who responded to NAC but still have residual disease in the axilla can be safely treated with SLNB(blue dye)+imaging-guided axillary approach and adjuvant RT. This approach eliminates the need for ALND in patients with low-volume residual axillary disease. Table. Patient characteristics Citation Format: Mahmut Muslumanoglu, Baran Mollavelioglu, Selman Emiroglu, Hasan Karanlik, Mustafa Tukenmez, Kamuran Ibis, Aysel Bayram, Ravza Yılmaz, Neslihan Cabıoğlu, Abdullah Igci. Imaging tailored axillary approach combined with radiotherapy eliminates axillary lymph node dissection in low-volume axillary disease after neoadjuvant chemotherapy 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 PO4-23-01.