Is Routine Axillary Imaging Necessary in Clinically Node-Negative Patients Undergoing Neoadjuvant Chemotherapy?

The National Comprehensive Cancer Network guidelines recommend axillary imaging prior to neoadjuvant chemotherapy (NAC) in breast cancer patients who are clinically node negative (cN0) by physical examination. However, the benefit of this approach remains uncertain. The purpose of this study was to determine whether abnormal axillary imaging pre-NAC predicts nodal metastases post-NAC (ypN+) in cN0 patients. cN0 patients undergoing NAC followed by axillary surgery were identified. Rates of ypN+ were compared among patients with abnormal pre-treatment axillary imaging vs. normal or no pre-treatment imaging using Fisher's exact test. From May 2008 to March 2016, 402 eligible cN0 patients were identified. The median age of the patients was 49.5 years, and the median tumor size was 4 cm. Of these patients, 38% were estrogen receptor-positive (ER+) and human epidermal growth factor receptor 2-negative (HER2-), 30% were HER2+ , and 32% were triple negative. All had pre-NAC mammograms, 40% axillary ultrasound, 83% MRI, and 51% PET. Abnormal nodes on imaging were seen in 208 patients (52%); 128 had pre-NAC node biopsy, and 75 were positive. Overall, 28% of the patients (n = 111) were ypN+ post-NAC. Although the incidence of ypN+ was significantly higher in patients with abnormal nodes on pre-NAC imaging (p = 0.001), 54% did not require axillary lymph node dissection (ALND) post-NAC. Among the patients with normal nodes on pre-NAC imaging, 20% were ypN+ post-NAC. Half of patients with abnormal nodes on pre-NAC imaging did not require ALND post-NAC, while 20% of those with normal pre-NAC nodes had disease post-NAC, indicating that in cN0 patients already selected for NAC, axillary imaging pre-NAC does not predict the need for axillary surgery post-NAC with sufficient accuracy to be clinically useful.