Abstract PS1-54: Risk factors for lymph node metastasis and the role of SLNB in microinvasive breast cancer

Introduction Incidence of microinvasive Breast cancer (DCISM) along with ductal carcinoma in situ is increasing due to mammographic screening. However, DCISM is not a common pathologic entity and surgical management of the axilla, overall treatment, and prognosis of this entity still remains unclear. Our study aims to determine whether sentinel lymph node biopsy (SLNB) is necessary for all DCISM patients and analyze the characteristics of lymph node-positive patients among DCISM patients to identify risk factors associated with lymph node metastasis. Materials and MethodsA total of 184,007 Breast cancer patients treated were registered in the Korean Breast Cancer Society Registry between 1978 to 2020. A retrospective review of the database was performed and the analysis includes diagnostic and clinic-pathologic characteristics such as positive lymph node and immunohistochemistry. A univariate analysis was carried out to determine associations between lymph node positivity and the clinical variables via Fisher’s exact test.ResultsOf the 184,007 patients, 2,556 (1.4%) breast cancer patients were classified as DCISM and 134 (5.2%) had at least one lymph node (node-positive), while 2,422 were node-negative patients. We found statistically significant results with hormone receptor status between node-positive and node-negative patients. Estrogen receptor (ER) and progesterone receptor (PR)-negative cases were associated with lower ORs (ER: OR=0.63, 95CI=0.43-0.92, P=0.016; PR: 0.67, 0.46-0.96, 0.026, respectively). A particularly interesting finding is that human epidermal growth factor receptor 2 (HER2)-negative cases were associated with higher OR (HER2: 2.03, 1.36-3.06, 0.001), suggesting hormone receptor status could be useful to identify potential lymph node metastases.ConclusionOur study suggests that we could omit axillary staging in DCISM patients, and consider optional SLNB in patients with ER, PR, and HER2 status with other overrepresented clinical entities such as palpable mass, BMI, and histologic grade.KeywordsMicroinvasive ductal carcinoma, Sentinel lymph node biopsy, lymph node metastasis Citation Format: Pill Sun Paik, Min Kyung Cho, Juneyoung Ahn, Chang Ik Yoon, Tae-Kyung Yoo, Woo-Chan Park. Risk factors for lymph node metastasis and the role of SLNB in microinvasive breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS1-54.