Abstract PS01-01: Feasibility and oncological safety of targeted axillary dissection or sentinel lymph node biopsy in patients with clinically node-positive disease after neoadjuvant chemotherapy in the prospective MF-1803 NEOSENTITURK-study

Abstract Background: Previous prospective studies reported decreased false negative rates in patients presenting with T1-3/cN1 disease, with the removal of 2 or more sentinel lymph nodes (SLNs), using combined technique for SLN biopsy (SLNB), and by targeted axillary dissection (TAD) in initially clinically node-positive patients after neoadjuvant chemotherapy (NAC). The aim of this prospective study is to compare the feasibility and the oncological safety of TAD with SLNB in patients with cN-positive/ycN0 breast cancer following NAC in a prospective study. Methods: This study included patients with a cT1-4N1-3M0 disease from the prospective multicenter MF1803 NEOSENTITURK registry study who were treated either SLNB- or TAD-alone without ALND. TAD included removing the biopsy-proven positive LN marked mostly with a clip as SLN or non-SLN. All patients had nodal and regional irradiation. Results: Between 2019 to 2021, 976 patients with cT1-4N1-3M0 disease from 37 centers underwent either SLNB-alone (n=620) or TAD-alone (n=356). Patients with TAD (median age: 46, range: 24-76) and SLNB (median age: 46, range: 21-80) have shown a similar age distribution. The median number (range, 25%-75%) of SLNs and total LNs and total metastatic LNs removed were 3 (2-4), 4 (3-6), and 1 (1-2), respectively. Patients with TAD were more likely to have cT1-2 disease (91. 9% vs 78. 7%, p 0. 001), cN1 disease (85. 7% vs 78. 5%, p 0. 006), a breast conservative surgery (66. 0% vs 51. 3%, p 0. 001), the combined technique for mapping (44. 1% vs 22. 3%, p 0. 0001), and a decreased median (IQR) lymph node ratio as calculated by the total positive lymph node number to the total lymph node number (0. 29: 0. 20-0. 40 vs 0. 33: 0. 20-0. 50; p=0. 033). Of note, there was a trend for the decreased non-sentinel lymph node positivity in the TAD-group compared to the SLNB-group that did not reach the statistical significance (TAD: 10% vs SLNB: 19%, p=0. 07). However, no significant difference could be found in pathological characteristics including tumor type, breast pCR, non-luminal disease such as HER2-positivity or triple negative disease or presence of low volume metastatic disease (ITC or micrometastasis), and extracapsular extension (Table 1). Of note, patients with ypN-positive disease (n=351) were more likely to have SLNs (ypN+, 3. 7±1. 7 vs ypN0, 3. 4±1. 7, p=0. 008) or total LNs (ypN+, 4. 7±1. 9 vs ypN0, 3. 4±1. 9, p=0. 001) removed compared to those with ypN0 (n=635). Among those with ypN0 disease, patients with TAD were more likely to have LNs removed compared to those with SLNB (TAD, 4. 2±1. 9 vs 3. 9±1. 9, p=0. 034) (Table 2). Of those with ypN+, patients with TAD were more likely to have SLNs compared to those with SLNB (TAD, 3. 9±1. 7 vs 3. 5±1. 7, p=0. 062), whereas patients with SLNB were more likely to have non-SLNs removed compared to those with TAD (TAD, 2. 3±1. 4 vs 2. 9±1. 5, p=0. 028). At a mean follow-up of 28. 8 months (±12. 1), the ipsilateral axillary and locoregional recurrence rates were 0. 2% (n=2) and 0. 4% (n=4) in the TAD-group and SLNBgroup, respectively. Of note, no significant difference could be found in ipsilateral axillary, locoregional, and systemic recurrences between cohorts treated with TAD-alone vs SLNB-alone (Table 3). Conclusion: Our findings suggest that TAD might be more feasible in ypN+ patients which resulted in a decreased lymph node ratio and decreased non-SLN positivity. In ypN0 patients, TAD may contrary cause unnecessary lymph node removal that might be important in arm function and lymphedema development. Furthermore, our findings with short-term follow-up indicate that axillary and locoregional recurrences were observed at very low rates in a selected group of ycN0 patients treated with SLN- or TAD without ALND. Therefore, omission of ALND could be safely considered for patients with limited nodal involvement (2 LNs) as long as 3 LNs removed and nodal radiotherapy provided. Table 1. Clinicopathologic Characteristics According to the Axillary Surgery: Targeted Axillary Dissection (=TAD) versus Sentinel Lymph Node Biopsy (=SLNB) Table 2. Clinicopathologic Characteristics According to the Pathological Nodal Status Table 3. Locoregional and systemic recurrences in cT1-4N1-3 patients treated with Targeted Axillary Dissection (=TAD) or Sentinel Lymph Node Biopsy (=SLNB) (Nf976) Citation Format: Neslihan Cabıoğlu, Hasan Karanlik, Mehmet Ali Gulcelik, Havva Belma Kocer, Mahmut Muslumanoglu, Abdullah İgci, Mustafa Tukenmez, Cihan Uras, Enver Ozkurt, Gokhan Giray Akgul, Selman Emiroglu, Süleyman Bademler, Ahmet Dağ, Didem Can Trabulus, Nilufer Yıldirim, Guldeniz Karadeniz Cakmak, Ebru Sen Oran, Halil Kara, Gul Basaran, Ayse Altinok, M. Umit Ugurlu, Kazim Senol, Baha Zengel, Niyazi Karaman, Ecenur Varol, Ece Dilege, Yasemin Bolukbasi, Alper Akcan, Yeliz Emine Ersoy, Aykut Soyder, Serdar Ozbas, Mehmet Velidedeoglu, Beyza Ozcinar, N. Zafer Utkan, Bulent Citgez, Burak Celik, Leyla Zer, Gurhan Sakman, Levent Yeniay, Lutfi Dogan, Mutlu Dogan, Fazilet Erozgen, BERK GOKTEPE, Orhan Agcaoglu, Taner Kivilcim, Fatih Levent Balci, Bahadir M. Gulluoglu, Ayfer Kamali Polat, Kamuran Ibis, Vahit Ozmen. Feasibility and oncological safety of targeted axillary dissection or sentinel lymph node biopsy in patients with clinically node-positive disease after neoadjuvant chemotherapy in the prospective MF-1803 NEOSENTITURK-study 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 PS01-01.