The use of ultrasound in the clinical re-staging of the axilla after neoadjuvant chemotherapy (NACT).

INTRODUCTION: Ultrasound (US) is the imaging modality of choice for staging the axilla prior to surgery in patients with breast cancer (BC). High pathological complete response rates in the axilla after NACT mean a more conservative approach to surgery can be considered. Radiological re-staging is important in this decision making. After the presentation of results from ACOSOG Z1071 in December 2012, formal ultrasound re-assessment of the axilla after primary therapy was specifically requested in our institution. We report on the accuracy of axillary US (aUS) for identifying residual axillary disease post-NACT.

METHODS: Data were collected on patients who had proven axillary disease prior to NACT and underwent axillary lymph node dissection after NACT between January 2013 and December 2015. Post-chemotherapy aUS reports and axillary pathology reports were classified as positive or negative for abnormal lymph nodes and for residual disease (cCR and pCR respectively).

RESULTS: The sensitivity and specificity of aUS was 71% and 88% respectively. The negative predictive value (NPV) was 83%. The false negative rate was 29%.

CONCLUSIONS: Axillary ultrasound provides clinically useful information post-NACT, which will guide surgical decision-making. Patients with aUS-negative axillae are likely to have a lower false negative rate of SLNB after NACT (Boughey et al.). However, aUS does not replace the need to identify and biopsy the nodes which were proven to be positive prior to NACT.