Abstract PS2-01-23: The accuracy of sentinel lymph node biopsy in locally advanced breast cancer

Abstract Introduction: Sentinel lymph node biopsy (SLNB) is the standard procedure for early breast cancer (BC), however its role in patients with locally advanced tumors (cT4N0) after neoadjuvant hormonal or chemotherapy remains a subject of discussion. The data on this type of patients is limited and the rate of false-negative results exceeds 10%/ Purpose of the study: to assess the diagnostic accuracy SLNB in patients with cT4N0M0 (ycN0) breast cancer after neoadjuvant therapy. Materials and methods: Our single-center prospective cohort study included 50 consecutive patients with cT4N0M0 breast cancer who received NALT followed by mastectomy with SLNB followed by level I-II axillary lymph node dissection (ALD). A radioguided method (99mTc-albumine nano colloid) was used to identify sentinel lymph nodes. The detection rate of sentinel lymph nodes, the level of false-negative results (FNR), sensitivity, and negative predictive value were evaluated. The univariate regression analysis was conducted to determine the factors that affect the frequency of false-negative results. Results: The detection rate was 96% (48/50). Metastatic lymph nodes were detected in 15 of 48 patients 31.3% during SLNB. After ALD metastasis were detected in 19 of 48 patients (39,5%). False negative rate (FNR) was 8,3% it the cohort. Sensitivity was 82,6%, Specificity 100%, and negative predictive value was 91,5%. Total accuracy was 92,3%. If 1 or 2 sentinel lymph nodes were removed FNR was 30,8% (4/13), if 3 or more lymph nodes were detected, FNR was 0% (0/35) (p=0,012). In univariate regression analysis only in the number of removed SLN increases the frequency of FNR. Patient’s age, BMI, molecular subtype, tumor grade, type of neoadjuvant therapy (chemo/hormonal) didn’t affect the accuracy of SLMB. Conclusion: The radioguided SLMB demonstrates acceptable diagnostic accuracy in patients with cT4N0 breast cancer after neoadjuvant therapy, which allows it to be an alternative to ALD, if at least three SLN are removed. Citation Format: A. Petrovsky, M. Kurbanova, M. Frolova, V. Amosova, E. Artamonova, I. Stilidi. The accuracy of sentinel lymph node biopsy in locally advanced breast cancer 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 PS2-01-23.