SP6.2 - Oncological outcomes following sentinel lymph node biopsy in patients with node positive breast cancer at diagnosis who achieve an axillary pathological complete response to neoadjuvant systemic therapy

Abstract De-escalation of axillary surgery following neoadjuvant chemotherapy (NACT) for patients with node positive breast cancer at diagnosis have focused on ensuring a low false negative rate for those who undergo sentinel lymph node biopsy (SLN) only with limited data to date on oncological outcomes. This study aimed to assess the medium-term oncological outcome in patients who have an axillary pCR following NACT and undergo de-escalation of axillary surgery with only a SLN performed post NACT. A consecutive series of patients with cytologically proven node-positive breast cancer who received NACT and achieved a nodal pCR on SLN between 2013-2021 were retrospectively analysed. Eligible patients underwent an end of treatment axillary ultrasound and if axillary nodes appeared sonographically normal a sentinel node biopsy was performed, with dual modality mapping (radioisotope and blue dye) at the time of breast surgery. The primary outcome of interest was disease free recurrence (DFS), and the secondary outcome was isolated axillary recurrence. 79 patients (median age 48 years) received NACT and had cytologically proven node-positive disease at diagnosis and attained an axillary pathological complete response (pCR) post NACT. The median nodal yield at SLN was 4 (range 1-9). Median follow up was 4.4 years. Only 1 patient experienced an axillary recurrence. Triple negative subtype had the lowest overall DFS. In this cohort, axillary recurrence remains uncommon. The optimal surgical strategy for safe de-escalation of axillary surgery post NACT remains in focus with adjuncts such as nodal marking and targeted axillary currently under study.