Clinical Utility of Ultrasound-Needle Biopsy for Preoperative Staging of the Axilla in Invasive Breast Cancer

Sentinel node biopsy (SNB) has largely replaced axillary lymph node dissection (ALND) as the standard-of-care for nodal staging in invasive breast cancer. Preoperative imaging-based staging of the axilla using ultrasound with selective ultrasound-guided needle biopsy (UNB) is moderately-sensitive and identifies approximately 50% of patients (pooled estimate from meta-analysis 50%; 95% confidence interval=43%-57%) with axillary nodal metastases prior to surgical intervention. It is also a highly specific staging strategy that allows patients to be triaged to ALND based on a positive result (positive predictive value approximates 100%), thus avoiding two-stage axillary surgery and unnecessary SNB. Axillary UNB has a good clinical utility: based on an updated meta-analysis, we found that a median proportion of 18.4% (inter-quartile range=13.3%-27.4%) from 7,097 patients can be effectively triaged to axillary treatment and can avoid SNB. However, the changing algorithm of axillary surgical treatment means that UNB will have relatively less utility where surgeons omit ALND for minimal nodal metastatic disease. Research that allows enhanced application of ultrasound and UNB to specifically identify and biopsy sentinel nodes and to discriminate between patients with minimal versus advanced nodal metastatic involvement is likely to have the most impact on future management of the axilla in breast cancer. In the context of continuing evolution of surgical treatment of the axilla, the status of the axillary nodes remains an important prognostic factor in patients with newly-diagnosed breast cancer, and of relevance to decision making on adjuvant systemic therapy. In the past, axillary lymph node dissection (ALND) was the standard-of-care for staging and treating the axilla in invasive breast cancer, however sentinel node biopsy (SNB) has replaced ALND as the primary approach. Emerging evidence on the omission of ALND in selected groups of patients with minimal sentinel node disease has added new debate and opportunities for staging the axilla, including preoperative methods. Given that surgical management of the axilla has changed considerably, so has the role of preoperative staging, in particular the inclusion of axillary ultrasound with ultrasound-guided needle biopsy (UNB). In the present work, we review the clinical utility of axillary ultrasound with UNB as an integrated staging strategy, factoring evidence on its accuracy and utility, as well as evidence on management of the axilla in invasive breast cancer, with emphasis on the role of preoperative testing and consequences in clinical decision-making.