Use of ultrasound and MRI to stage the axilla for breast cancer before and after neoadjuvant chemotherapy prior to targeted sentinel lymphadenectomy.

ABSTRACT

PURPOSE: Prior data from this Center demonstrated that for patients who had biopsy-proven axillary metastases, were ycN0 after neoadjuvant chemotherapy (NAC), and had a wire-directed (targeted) sentinel lymphadenectomy (WD-SLND), 60% were node negative. The hypothesis of this study was that results of axillary imaging either before or after NAC would be predictive of final pathologic status after WD-SLND. METHODS: For patients treated with NAC between 2015 and 2023, ultrasound and MRI images of the axilla were retrospectively reviewed by radiologists specializing in breast imaging, who were blinded to the surgical and pathology results. RESULTS: Of 113 patients who fit the clinical criteria, 66 (58%) were ypN0 at WD-SLND and 34 (30%) had a pathologic complete response to NAC. There was no correlation between the number of abnormal lymph nodes on pre-NAC ultrasound or MRI imaging and the final pathologic status of the lymph nodes. The positive predictive value (PPV) of abnormal post-NAC axillary imaging was 48% for ultrasound and 53% for MRI. The negative predictive value (NPV) for normal post-NAC axillary imaging was 67% for ultrasound and 68% for MRI. CONCLUSION: The results of axillary imaging were not adequate to identify lymph nodes after NAC that were persistently pathologically node positive or those which had become pathologically node negative.