Abstract PS2-06-07: The Necessity of Sentinel Lymph Node Biopsy for Ductal Carcinoma in Situ Patients: a Retrospective Analysis of a Single Institute in Taiwan

Abstract Purpose: Ductal carcinoma in situ is the preliminary phase of invasive breast cancer, with lesions confined within the mammary ducts, and have limited extensiveness. Owing to its non-invasive feature, axillary lymph node involvement is typically non-existence. Therefore, under current guidelines and consensus adopted worldwide, lymph node management is not a mandated procedure. However, the risk of clinical diagnosis of in situ carcinoma upstaging to invasive carcinoma after definitive surgery is still menacing, with some reported upstaging rates exceeding 30%. Nowadays, sentinel biopsy for node staging is generally not recommended for ductal carcinoma in situ patients receiving breast conservative surgery, however, such procedure is sometimes carried out nevertheless for various individualized reasons. Our study aims to report our real-world clinical experience on such unmet need, hoping to aid in the precise assessment of sentinel lymph node biopsy indication for such patients. Materials and Methods: Patients with a clinical diagnosis of ductal carcinoma in situ admitted to a single institute in Taiwan from 2019 to 2023, who have received definitive surgery with final pathological outcomes were gathered. Various clinical features including patient characteristics, tumor palpability, sonographic tumor size, biopsy methods, ductal carcinoma in situ tumor grading, immunohistochemistry results were evaluated. Sentinel lymph node positive rate and cancer upstaging rate were our primary outcomes. We analyze the risk factors contributing to in situ carcinoma upstaging. Results: Within 203 enrolled patients with clinical biopsied diagnosis of ductal carcinoma in situ, 55 patients (27.1%) were upstaged to invasive carcinoma in surgical pathology. Concurrent sentinel lymph node biopsy during definitive surgery was performed in 172 patients (84.7%), and nodal metastasis was found in 4 cases (2.3%). Among the 31 enrolled patients who omitted sentinel lymph node biopsy, 3 patients (9.7%) had upstaged to invasive disease. Regarding characteristic features analyzed, age over 50 years (OR: 1.703, p=0.028), diagnosed by core needle biopsy rather than by vacuum-assisted or excisional biopsy (P<0.001), sonographic tumor size greater than 2cm (OR: 1.733, p=0.016), and HER2 receptor negativity (OR: 1.377, p<0.001), showed significant risk of upstaging. Conclusion: Sentinel lymph node biopsy is not routinely carried out for ductal carcinoma in situ patients according to current treatment consensus. Whereas cancer upstaging is the least desirable situation after definite surgery. We disclosed Taiwan’s real-world data to clarify the necessity of sentinel lymph node biopsy for certain patients. We believe, thorough discussion and shared decision making between surgeon and patients before surgery is crucial, and sentinel lymph node staging could be provided as an option to the highly selected individuals with significant upstaging risk, eliminating the distress of under-treatment and re-operation for the patient. Citation Format: Y. Chen, S. Shih, M. Hou, F. Chen, C. Li, J. Kan, C. Kao, L. Kao, H. Takahashi, C. Chuang, C. Kuo, P. Yang. The Necessity of Sentinel Lymph Node Biopsy for Ductal Carcinoma in Situ Patients: a Retrospective Analysis of a Single Institute in Taiwan [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 PS2-06-07.