EP.TH.930Contemporary trends in the management of micrometastatic axillary disease in the setting of mastectomy – a 5 year single institution experience

Background Since the ACOSOG Z0011 trial, rates of axillary node clearance (ANC) for micrometastatic axillary disease have declined among women undergoing breast conservation surgery (BCS). However, for women undergoing mastectomy, it remains unclear whether omission of ANC is a safe and feasible option. Aims Identify current practice relating to management of the axilla in women with early stage, clinically node negative breast cancer, found to have micrometastatic disease on SNB, who undergo mastectomy Methods From 2013 to 2017 patients with clinical T1-T2Nmi breast cancer undergoing upfront surgery were identified from a prospective institutional database. Receipt of adjuvant radiotherapy or subsequent ANC were assessed. Patients who received neoadjuvant chemotherapy or BCS were excluded. Results 47 patients undergoing mastectomy for ESBC had micrometastasis identified on SNB. The majority of tumours had invasive ductal histology. 16/27 women underwent completion ANC (34%). Six patients had further nodal disease identified in the ANC specimen. 2 had >5 nodes positive. During the study period 31 patients (65%) received adjuvant radiotherapy. Of the patients who did not undergo ANC, 21 (67.7%) received adjuvant radiotherapy. Conclusion At this institution the majority of patients requiring mastectomy with micrometastatic disease on SNB do not undergo subsequent ANC (>60%). Although this is a small patient cohort, these data indicate the rate of residual axillary disease is low, and are in keeping with trends in the literature, and may help inform management decisions in this patient group.