Abstract PS2-03-03: Retrospective analysis of axillary recurrence in patients with breast cancer receiving radiotherapy to the axillary after positive sentinel lymph node biopsy

Abstract Background: Breast cancer surgery currently focuses on de-escalating treatment without compromising oncological safety. Axillary lymph node dissection (ALND) has been the standard of care in all sentinel lymph node biopsy (SLNB) positive patients. Although axillary lymph node dissection provides excellent regional control, there are additional side effects like lymphoedema, shoulder stiffness, numbness in the arm. Studies show axillary radiotherapy is an alternate and equally effective treatment for SLNB-positive patients with reduced morbidity. However, this is not a standard of practice in all breast centers in UK. Methodology: A retrospective, single center study between June 2015 and June 2022 following the results published from AMAROS (After Mapping of the Axilla: Radiotherapy Or Surgery) trial in 2014. All patients with breast cancer and clinically and radiologically negative axilla underwent SLNB along with either breast conserving surgery or mastectomy as a routine procedure. Patients with positive SLNB were later offered further axillary management (ALND vs Axillary radiotherapy). Patients who opted for axillary radiotherapy were then analyzed in a retrospective study. Patients’ demographics, disease distribution, nodal positivity, adjuvant treatment were studied. The primary end point was axillary recurrence at the end of 5 years (in line with the AMAROS trial i.e. not more than 4% in axillary radiotherapy group). The secondary end point was arm morbidity and overall survival. Results: A total of 186 patients had positive sentinel lymph node biopsy during the study period and out of them 112 patients, opted for axillary radiotherapy as their mainstay of axillary management. 40(35.7%) patients had T1 disease, 57(50.89%) patients had T2, and 15(13.39%) patients had T3 disease. 13.39% had Grade1 disease, 53.57% had Grade2, and 33.92% had Grade 3 disease. The median number of nodes being 1. The mean age was 63 years, and the mean tumor size of 14.33mm. The mean follow-up was 5.58 years. Axillary recurrence was seen in 3 patients (2.67%), and 1 patient (0.89%) developed lymphedema. 9 patients (8.03%) had distant metastasis. Death due to breast cancer was slightly lower in our study as compared to AMAROS trial (7.84% vs 10.3%) and similar overall death rates (19.04% vs 16.4%) Conclusion: Our study shows that the 5-year axillary recurrence rate is comparable with the AMAROS trial (2.76% vs 1.19%) with similar follow up period (5.58years vs 6.1years). Our study has limitations of small numbers but aligns well with the AMAROS trial. Hence, axillary radiotherapy is non-inferior to axillary lymph node dissection in patients with positive SLNB with significantly less morbidity. Citation Format: C. Gavisiddappa, R. Parmeshwar, P. McManus, S. Somasundaram. Retrospective analysis of axillary recurrence in patients with breast cancer receiving radiotherapy to the axillary after positive sentinel lymph node biopsy 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 PS2-03-03.