SRS125 - Sentinel lymph node biopsy as a determinant of adjuvant therapy in breast cancer

Abstract Introduction Data from SOUND and INSEMA trials demonstrate that sentinel lymph node biopsy (SLNB) can be safely omitted in select breast cancer patients. Aim This study aimed to determine utility of SLNB in guiding adjuvant management for patients with breast cancer, in the form of de-escalating or escalating therapy. Methods A retrospective analysis of patients diagnosed with breast cancer between December 2013 and March 2024 in a large centre in Ireland was conducted. Inclusion criteria included: female patients, ≥18years, with cT1 tumours, a negative pre-operative axilla, who underwent breast conserving surgery and SLNB. Results In total, 334 patients were included in the final analysis. The median age was 59 years (26–91 years). The majority had invasive ductal carcinoma (261 patients, 78.1%) and were HR+/HER2− (274 patients, 82%). Final N stage was N0 in 282 (84%) of patients. Fifty-two patients (16%) had a positive SLNB, despite a negative pre-operative axilla. Twenty-four patients underwent an axillary clearance, of which 7 (14%) were positive, with 3 patients (12.5%) upstaged following axillary clearance. Eighty-four patients (25%) received chemotherapy due to their positive SLNB status. In line with contemporary data, 9 patients (2.7%) were eligible for CDK4/6 inhibitors, 48 patients (14%) for escalation to nodal radiation, or 275 patients (82%) for de-escalation to partial breast radiation. Conclusions Despite nodal upstaging following axillary dissection being uncommon, SLNB, whether positive or negative, facilitates evidence-based escalation or de-escalation of local and systemic therapy in breast cancer, thus supporting its continued use.