The use of axillary ultrasound (AUS) to assess the nodal status after neoadjuvant chemotherapy (NACT) in primary breast cancer patients

Introduction: Axillary Ultrasound (AUS) is standard for pre-therapeutic axillary staging in early breast cancer patients. 35-75 % of the breast cancer (BC) patients with positive axillary lymph nodes receiving neoadjuvant chemotherapy (NACT) convert to pathological node negative. For those patients, axillary surgery after NACT could be de-escalated, if an accurate prediction of the pathologic nodal status following NACT was possible. This study aims to answer the question, whether AUS can be used as a reliable diagnostic tool for restaging of axillary nodal status after NACT.

Patients and methods: We collected data of 96 patients with nodal positive primary breast cancer who received NACT between 2009 and 2015 at the Breast Cancer Center of the University Hospital Ulm. Patients were classified as node negative or positive by AUS after NACT (ycN + or ycN0) and the results were compared to the pathological result obtained after axillary lymph node dissection (ypN + vs ypN0) in all patients.

Results: 58.3 % of the patients had pathological complete remission of axillary lymph nodes after NACT (ypN0). The sensitivity and specificity of AUS were 57.5 % and 78.6 %, respectively. The FNR was 42.5 %. The Positive and Negative Predictive Values (PPV and NPV) were 65.7 % and 72.1 %, respectively. The accuracy of AUS was 69.8 % and not associated with any of the investigated clinico-pathological parameters.

Conclusion: AUS alone is not accurate enough to replace surgical restaging of the axilla after NACT in initially node positive breast cancer patients.