Abstract PD15-01: PD15-01 AXILLARY NODAL RECURRENCE IS RARE IN PATIENTS WITH NODE-POSITIVE BREAST CANCER UNDERGOING SLNB FOLLOWING NEOADJUVANT CHEMOTHERAPY : EARLY RESULTS OF THE NEOSENTITURK-TRIAL/MF-18-03

Abstract Background: Whether axillary lymph node dissection (ALND) following sentinel lymph node biopsy (SLNB) could be spared in patients with initially clinically positive axilla after neoadjuvant chemotherapy (NAC) is still controversial even though recent studies indicate that axillary recurrence seems to be a rare event. Our aim is to find out whether omitting ALND could be oncologically safe in patients undergoing SLNB after NAC. Material and Methods: Of patients presented with c T1-4N1-3M0 disease, those undergoing SLNB after NAC were included in the prospective multicentre registry trial " MF18-03/BHWG" (ClinicalTrials.gov/NCT04250129). Cases with inflammatory breast cancer, distant metastases, pregnancy, bilateral breast cancer, or other cancers and those without adjuvant nodal radiotherapy were excluded from the study. The end points of the present report are the axillary nodal recurrence (AR) and locoregional recurrence (LRR) rates at a median follow-up more than 2 years, and determine factors associated with AR and LRR . The locoregional recurrences included ipsilateral, and contralateral axillary recurrences, infra-and supraclavicular recurrences, and recurrences in the mammaria interna region. Results: Between January 2018 to January 2021, 2358 patients with cN(+) disease, who became cN0 after NAC, and underwent SLNB, were analyzed. Median age was 47 (range, 21-86). Of those, the majority of patients had cT1-2 (80.5%) and N1 (80.3%) disease. Following NAC, half of the patients (50%) had breast conserving surgery, whereas the remaining half had mastectomy (50%). Of 2358 patients, 908 (38.5%) had ALND following SLN (ypN+, 85%) and 1450 (61.5%) underwent SLNB alone (ypN0, 72%). SLNB was performed by using the blue dye technique-alone in 66.6% of patients and by targeted axillary dissection in 659 patients (27.9%). Of those, 819 (34.8%) were HER2(+) and 373 (15.8%) were triple negative. The pCR rates for the axilla, breast and both for the axilla and breast were 50%, 35% and 28%, respectively. At a median follow-up time of 28 months (range, 12-62), the LRR, AR and isolated AR rates were 0.6% (n=14), 0.25% (n=6) and 0.13% (n=3), respectively. Furthermore, no significant difference could be found in LRR- and AR- rates between SLNB-alone and ALND groups regardless of the definitive nodal pathology (Table 1). Nodal recurrences were seen at a median of 12 months after the surgery. Of 6 cases with AR, 3 had synchronous local recurrences in breast, and 2 of them also had lung metastases in addition to local recurrence. All patients with AR were interestingly found to have HER2(+) or triple negative breast cancer at the initial diagnosis, and had residual invasive cancer in the breast surgical specimen. Logistic regression analyses revealed that patients with AR were significantly more likely to be younger than 45 (RR=7.81 ; 95% CI, 0.91-66.91) and have a cN2-3 (RR=4.1; 95% CI, 0.83-20.38), and non-luminal breast cancer (RR=12.47; 95% CI, 1.45-106.9) at the initial diagnosis (Table 2). Similarly, patients with LRR were more likely to present with cN2-3 disease (RR=3.09; 95% CI, 1.07-8.94) and non-luminal pathology (RR=6.27; 95%CI, 1.96-20.06) . Conclusion: This large prospective registry data also suggest that nodal recurrences can be detected at very low rates within 3 years after surgery in patients with clinically node-positive disease following NAC regardless of the extent of axillary surgery or nodal pathology as long as regional nodal radiation is provided. Since patients with early nodal recurrences have an agressive tumor biology with a potential of systemic recurrences, effective adjuvant systemic therapies should be considered in those with HER2(+) or triple negative residual breast cancer after surgery following adjuvant nodal radiation. Table 1. Local locoregoinal and systemic recurrences in cT1-4N1-3 patients with ypN0/ypN(+) diseases (n =2358) Table 2. Factors associated with axillary and locoregoinal recurrences (AR = axillary recurrences, LRR = locoregoinal recurrences, pCR = pathologic complete response) Citation Format: Neslihan Cabıoğlu, Hasan Karanlik, Mehmet Ali Gulcelik, Abdullah İgci, Mahmut Muslumanoglu, Havva Belma Kocer, Cihan Uras, Gokhan Giray Akgul, Mustafa Tukenmez, Serkan Ilgun, Didem Can Trabulus, Guldeniz Karadeniz Cakmak, Ahmet Dağ, Nilufer Yıldirim, Baha Zengel, Ebru Sen Oran, Kazim Senol, Halil Kara, Selman Emiroglu, M. Umit Ugurlu, Bulent Citgez, Yeliz Emine Ersoy, Atilla Celik, Ece Dilege, Yasemin Bolukbaşı, Niyazi Karaman, Gul Basaran, Aykut Soyder, Ayfer Kamali Polat, Gurhan Sakman, Serdar Ozbas, Ayse Altınok, Leyla Zer, Alper Akcan, Ibrahim Ali Ozemir, Levent Yeniay, N. Zafer Utkan, Lutfi Dogan, Mutlu Dogan, Mehmet Velidedeoglu, Beyza Ozcinar, Fazilet Erozgen, Abut Kebudi, Kemal Atahan, Vafa Valiyeva, Serdar Yormaz, Ali Sevinc, Cumhur Arici, Atilla Soran, Vahit Ozmen. PD15-01 AXILLARY NODAL RECURRENCE IS RARE IN PATIENTS WITH NODE-POSITIVE BREAST CANCER UNDERGOING SLNB FOLLOWING NEOADJUVANT CHEMOTHERAPY : EARLY RESULTS OF THE NEOSENTITURK-TRIAL/MF-18-03 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD15-01.