Abstract PS1-19: The accuracy of axillary node assessment of ultrasound after neoadjuvant chemotherapy in clinically node positive patients

Abstract

Abstract Background. Neo-adjuvant chemotherapy (NAC) is widely used as preoperative systemic therapy for operable breast cancer. However, the use of sentinel-lymph-node biopsy (SNB) following NAC for patients with clinically node positive is controversial, even if they achieve cCR in the axilla. Although preoperative axillary imaging assessment may help to decide axillary management after NAC, few data are available on whether axillary ultrasound (LN-US) is useful to assess axillary response to NAC. Purpose. We investigated the accuracy of axillary node assessment by ultrasound after NAC in clinically node positive patients and analyzed factors related to the accuracy of LN-US. Methods. From January 2012 through December 2016, patients with cT1-4, N1-2, M0 primary breast cancer who had cytologically proven axillary metastasis, and underwent axillary lymph node dissection (ALND) after NAC were retrospectively reviewed. Clinically positive lymph node by LN-US was defined as concentric cortical thickness >3mm, absent fatty hilum, or irregular morphology. Results. A total of 298 patients with clinical stage T1-4, N1-2, M0 primary breast cancer who had cytologically proven axillary metastasis, and underwent surgery with axillary dissection following NAC were enrolled. Of 279 eligible patients, 101 patients (36.2%) showed pathologically node-negative in the axilla (ypN0), and the rate of ypN0 was 20.2% (37/183) in hormone receptor (HR)+/human epidermal growth factor receptor-2 (HER2)-, 71.9% (23/32) in HR+/HER2+, 83.3% (20/24) in HR-/HER2+, and 52.5% (21/40) in HR-/HER2-. Sensitivity and specificity of LN-US were 65.7% and 62.3% respectively. The accurate prediction rate of node-negative status after NAC by LN-US was 49.2% in total, 29.7% in HR+/HER2-, 89.5% in HR+/HER2+, 86.7% in HR-/HER2+, and 68.8% in HR-/HER2- disease. The accuracy was highest in the HER2+, and lowest in HR+/HER2-. The median number of pathologically positive residual nodes at ALND after NAC was 2 (1-16) in total and 2 (1-15) in patients with ycN0. Of 61 patients with ycN0ypN+, 26 (42.6%) had 1 positive lymph node on the pathologic review, 9 (14.8%) had 2 positive lymph nodes, 7 (11.5%) had 3 positive lymph nodes, and 19 (31.1%) had more than 3 positive lymph nodes.The accuracy of node negative status by LN-US varies significantly by tumor subtype (p<0.001) and tumor response as assessed by MRI after completion of NAC (p=0.0003), although there was no significant difference between two groups regarding T category at diagnosis, tumor histology, and the number of positive nodes before NAC as assessed by LN-US. Of 23 patients who achieved ycN0 in LN-US and cCR in the primary lesion in MRI, the accurate prediction rate of ypN0 was 100% in patients with HR±/HER2+ and HR-/HER2- disease. Conclusion. The accuracy of axillary US after NAC depended on subtypes, which was highest in the HER2 disease and the accuracy increased by combing with the tumor response in the breast assessed by MRI. In the point of reducing FNR after NAC by LN-US assessment before surgery, the accuracy of NPV is especially important. We suggest that it is of clinical importance to take account of tumor subtypes and primary tumor response in the breast by MRI in combination with LN-US in selecting patients for SNB after NAC. Citation Format: Yurina Maeshima, Takehiko Sakai, Akiko Ogiya, Yoko Takahashi, Yumi Miyagi, Takayuki Ueno, Shinji Ohno. The accuracy of axillary node assessment of ultrasound after neoadjuvant chemotherapy in clinically node positive patients [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS1-19.