Abstract PS2-03-28: An Investigation to Identify the Factors for Negative Sentinel Lymph Node in Early Breast Cancer Cases

Abstract Background: Sentinel Lymph Node Biopsy (SLNB) in breast cancer is a standard procedure used to determine whether breast cancer has spread to the axillary lymph nodes. It has replaced full axillary lymph node dissection (ALND) in early-stage clinically node-negative (cN0) breast cancer patients. However, SLNB is associated with some rare complications such as pain, seroma and lymphedema. Omission of SLNB in breast cancer is an evolving area in clinical practice and may be a safe and reasonable option. To identify cases in which SLNB was negative, we conducted a retrospective study using early breast cancer data from our hospital registry. Methods: A total of 2,589 breast cancer patients underwent SLNB between June 2016 and April 2025. Of these, 1,956 cases of cN0 invasive breast cancer who did not undergo preoperative chemotherapy were included in this retrospective study. Pathological diagnosis using frozen section or one-step nucleic acid amplification (OSNA) method was used for the diagnosis of SLNs. The number of SLNs examined ranged from 1 to 7, with a mean of 1.8 nodes. The disease-free survival (DFS) was calculated using the Kaplan-Meier method and analyzed using the log-rank procedure. The multivariate analysis of factors for negative SLN was performed using logistic regression analysis. Results: 1. Metastasis to the SLNs was observed in 379 cases (19.4%) including micro-metastasis. The median number of metastatic SLN was 1.0. SLN metastasis was observed in 139 (14.5%) cases with breast conserving surgery (Bp) and 240 (24.1%) cases with total mastectomy (Bt). Of cases with positive SLN, 378 cases (87.9%) received ALND. 2. Cases with invasive ductal carcinoma (IDC) had a 19.9% positive SLN rate and cases with invasive lobular carcinoma (ILC) and invasive micropapillary carcinoma (IMPC) had higher positive rates than IDC. 3. SLN metastasis was not associated with ER, PgR and HER2 status. However, significant differences were observed in age, tumor size, Ki-67 index value and histological grade. The incidence of SLN metastasis was significantly lower in patients aged 50 years or older (postmenopausal), a tumor size of 2 cm or less, a Ki-67 index value 15%, and a histological grade (HG) of 1. 4. A multivariate analysis was performed on the above-mentioned factors to determine the factors related to negative SLNs. The significant factors were age, tumor size and HG, and only a marginal significance was found in the Ki-67 index value. 5. The incidence of SLN metastasis in Luminal B type was significantly higher than the other subtypes. 6. The postoperative 7- year DFS rate of cases 50 years of age, a tumor size of ≤ 2 cm and a HG of 1 was favorable regardless of the presence or absence of SLN metastasis (99.5% for negative SLN and 100% for positive SLN). Conclusion: Metastasis to SLN was found in 19.4% of cN0 breast cancer cases. Factors related to negative SLN were age (50 years or older), tumor size (2cm or less), and HG (1), and the positive SLN rate was significantly higher in cases with the Luminal B subtype. The prognosis for cases with the above factors was good, and recurrences were rarely observed. In the future, whether SLNB is required will depend on the above-mentioned patient characteristics. Citation Format: R. Nishimura, Y. Ueda, K. Kiyohara, M. Funagayama, N. Ikeda, A. Kato, H. Tokiniwa, R. Higashi, M. Nakahara, H. Ifuku, T. Hayashi, Y. Sagara, Y. Sagara, S. Ohno. An Investigation to Identify the Factors for Negative Sentinel Lymph Node in Early Breast Cancer Cases abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-03-28.