Abstract PS2-05-08: Refusal of sentinel lymph node biopsy in patients with luminal A subtype early breast cancer

Abstract Background: The indications for and extent of axillary surgery in breast cancer have evolved significantly over the past two decades and remain an area of active research and debate. Sentinel lymph node biopsy (SLNB) is currently the standard approach for axillary staging in patients with early-stage breast cancer. However, emerging data suggest that axillary surgery may be safely omitted in select patients aged ≥60 years with early-stage, luminal A, clinically node-negative breast cancer. This prospective study aimed to assess the applicability of this strategy in patients with hormone receptor-positive (HR+), HER2-negative (HER2−) tumors. Method: This prospective study included 100 patients diagnosed with cT1-2N0M0, HR+HER2- breast cancer (BC) who underwent combined treatment from 2023 to 2025 at the FSBI «N.N. Petrov National Medical Research Center of Oncology» of the Russian Ministry of Health. All patients had clinically negative axillary lymph nodes confirmed via ultrasound, mammography and mammoscintigraphy/breast molecular imaging with 99mTc-MIBI. Surgical axillary staging was omitted in this patient population. Preoperative sentinel lymph node localization for adjuvant radiation treatment planning was performed using single-photon emission computed tomography (SPECT) lymphoscintigraphy. Results: Among 100 patients with cT1-2N0M0 HR+HER2- breast cancer median age was 67 59; 86 years. Median tumor size was 15 4; 30 mm and tumors were grade 1 or 2. Estrogen receptor (ER) expression ranged from 90-100% in 95 cases and 70-80% in 5 cases. Progesterone receptor (PR) expression was 0-10% in 17 cases, 20-40% in 4, and 60-100% in 79. The Ki-67 proliferation index was 1-10% in 29 cases, 11-20% in 46, and 21-30% in 25. Histological subtypes included 94 cases of invasive carcinoma of no special type (NST), 3 - lobular carcinomas, and 3 - mucinous carcinomas. All patients in the study received adjuvant radiotherapy, administered in hypo- or ultra-hypofractionation regimens at the discretion of the radiation oncologist for breast and sentinel lymph nodes. Specifically, 15 patients received a 5-fraction regimen, 50 patients received 15 fractions, 35 patients received 16 fractions, and 2 patients underwent high-dose brachytherapy additionally. Adjuvant hormone therapy was recommended for all patients: 79 received Aromatase Inhibitors and 21 received Tamoxifen. No patient was recommended to receive adjuvant chemotherapy. Conclusion: We believe that these findings support careful implementation of omission of surgical staging of the axilla in postmenopausal patients with cT1-2N0, HR+HER2− breast cancer and a negative axillary lymph nodes. At our institution, this approach is currently implemented in patients over 59 years of age with ECOG performance status 3, tumor grade 1-2, ER expression 20%, and Ki-67 index 30%. Citation Format: A. O. Gorina, P. V. Krivorotko, A. S. Emelyanov, D. A. Enaldieva, E. K. Zhiltsova, L. P. Gigolaeva, T. T. Tabagua, A. V. Komyakhov, V. V. Mortada, P. S. Pesotsky, D. G. Ulrikh, N. S. Amirov, V. F. Semiglazov. Refusal of sentinel lymph node biopsy in patients with luminal A subtype early 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 PS2-05-08.