Objectives: To (a) determine the diagnostic validity of axillary ultrasound (AUS) in pT1 tumours and whether fine-needle aspiration (FNA) improves its diagnostic performance, and (b) determine the negative predictive value (NPV) of AUS in a simulation environment (cutoff: two lymph nodes with macrometastases) in patients fulfilling American College of Surgeons Oncology Group (ACOSOG) Z0011 criteria.
Materials and methods: This retrospective multicentre cross-sectional study analysed diagnostic accuracy in 355 pT1 breast cancers. All patients underwent AUS; visible nodes underwent FNA regardless of their AUS appearance. Sentinel node biopsy and axillary lymph node dissection (ALND) were gold standards. Data were analysed considering micrometastases 'positive' and considering micrometastases 'N negative'. The simulation environment included all patients fulfilling ACOSOG Z0011 criteria.
Results: Axillary involvement: 22.8 %; AUS sensitivity: 46.9 % (Nmic positive)/66.7 % (Nmic negative); AUS+FNA sensitivity: 52.6 % (pNmic positive)/72.0 % (pNmic negative). In the simulation environment, AUS had 75.0 % sensitivity, 88.9 % specificity and 99.2 % NPV.
Conclusion: AUS has moderate sensitivity in T1 tumours. As ALND is unnecessary in micrometastases, considering micrometastases 'N negative' increases the practical impact of AUS. In patients fulfilling ACOSOG Z0011 criteria, AUS alone can predict cases unlikely to benefit from ALND.
Key points: • AUS+FNA can predict axillary involvement, thus avoiding SNB. • Not all patients with axillary involvement need ALND. • Axillary tumour load determines axillary management. • AUS could classify patients according to axillary load.
Keywords: Axillary surgery; Axillary ultrasound; Breast cancer; Percutaneous biopsy; Sentinel lymph node biopsy.