Abstract PS01-03: What to expect from the No axillary surgical treatment for lymph node-negative patients after ultra-sonography NAUTILUS trial (KBCSG-21): Clinicopathologic characteristics and axillary lymph node status of enrolled patients

Abstract Purpose: The primary role of sentinel lymph node biopsy (SLNB) for early breast cancer (BC) is axillary staging. In terms of clearance of axillary disease or prevention of recurrence, its role may be limited considering the low axillary recurrence rate of less than 2% even though false-negative rates are 5-10% and the 25% additional axillary lymph node (ALN) detection in the ALND arms of the ACOSOG Z0011 and AMAROS trials. The NAUTILUS trial (NCT04303715) randomized cT1-2/N0 BC patients planned for breast-conserving surgery to evaluate the non-inferiority of omitting SLNB regarding 5-year invasive disease-free survival. The secondary endpoints are overall survival, distant metastasis-free survival, axillary recurrence rate, and quality of life of the patients. We aimed to investigate the clinicopathologic characteristics and ALN status of the subjects enrolled in the NAUTILUS trial. Methods: NAUTILUS trial randomized 1,734 subjects into SLNB or no-SLNB arms from September 2020 to October 2022. Axillary ultrasonography was mandatory to determine clinical N0, defined as no suspicious ALN or no tumor on ultrasound-guided biopsy of suspicious ALN. Clinicopathologic variables and the ALN status of the SLNB arm were analyzed. Results: Among 1,734 enrolled subjects, 828 (50.3%) and 818 (49.7%) subjects in the SLNB and no-SLNB arms, respectively, were included for analysis. Clinical and pathologic T stage, hormonal receptor/HER2 status, histologic grade, age, menopausal status, and Ki-67 were evenly distributed between the two groups (p = 0.554, 0.350, 0.056, 0.369, 0.623, 0.725 and 0.214, respectively). Median age was 55.3 (range, 48.0-62.0) years, and 661 (40.2%) were premenopausal. Overall, 30 (1.8%), 1,382 (84.0%), and 229 (13.9%) subjects were pTmic, pT1, and pT2, respectively, and median tumor size was 1.3 cm (range, 0.1-5.0). In the SLNB group, 94 (11.4%) had ALN metastasis, of which 9 (1.1%), 78 (9.4%), and 5 (0.6%) were pN1mic, pN1, and pN2-3, respectively (Table 1). According to pathologic tumor size, 5.8% (16/279), 11.4% (48/421), and 23.8% (30/126) were ALN positive for ≤ 1.0 cm, 1.0cm 2.0 1.0cm 2.0 LVI, lymphovascular invasion; IDC, invasive ductal carcinoma; ILC, invasive lobular carcinoma; HER2, anti-human epidermal growth factor-2; BCS, breast conserving surgery; TM, total mastectomy; ALND, axillary lymph node dissection Basic characteristics for sentinel lymph node biopsy group a revealed no lymph node metastasis by fine needle aspiration or gun biopsy ALN, axillary lymph node; LN, lymph node Citation Format: Jai Min Ryu, Han-Byoel Lee, Sei Hyun Ahn, Il-Yong Chung, Seeyoun Lee, Seho Park, Woosung Lim, Joon Jeong, Jeong Eon Lee, Eunhye Kang, Ji Hyun Chang, Jung Min Chang, Woo Kyung Moon, Wonshik Han, Eun-Kyu Kim. What to expect from the No axillary surgical treatment for lymph node-negative patients after ultra-sonography NAUTILUS trial (KBCSG-21): Clinicopathologic characteristics and axillary lymph node status of enrolled patients 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 PS01-03.