Background: Although surgical management of the breast after neoadjuvant chemotherapy (NAC) may be governed by treatment response, axillary management continues to be determined by stage at presentation. Axillary ultrasound (AUS) with fine-needle aspiration (FNA) is used to detect lymph node (LN) metastases for pre-NAC staging, but imaging assessment of treatment response in the axilla remains undefined. We evaluated post-NAC axillary imaging and surgical pathology to understand how imaging might direct axillary surgery. Methods: We evaluated pre- and post-NAC axillary imaging and clinicopathologic data in 272 patients who received NAC for primary breast cancer and underwent operation at our institution from 2010 to 2012. Treatment response on imaging was categorized as complete (CR), partial (PR), and none/progression (NR). Results: Pre-NAC axillary staging classified patients as AUS negative/no FNA (n = 61), FNA/LN negative (n = 42), and FNA/LN positive (n = 169). Post-NAC axillary imaging included AUS (n = 146), MRI (n = 139), and PET-CT (n = 38). At operation, 128 of 272 patients (47 %) were LN positive: 23.3 % (24 of 103) of cN0 and 61.5 % (104 of 169) of cN1-AUS/FNA-positive patients at presentation. Of the 65 cN1-ypN0 patients, 58.1 % (25 of 43) had an imaging CR by US, 58.6 % (17 of 29) by MRI, and 84.6 % (11 of 13) by PET-CT. The sensitivity of post-NAC axillary imaging in detecting persistent LN metastases for cN1-AUS/FNA-positive patients was 69.8 % for US, 61.0 % for MRI, and 63.2 % for PET-CT. Conclusions: Performance characteristics of AUS, MRI, and PET-CT, while informative, were inadequate to preclude surgical axillary staging of in breast cancer patients after NAC. Whether this information might be used to tailor surgical and postsurgical treatment requires further investigation.
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