Abstract P5-01-05: A Predictive Model for Axillary Pathologic Response after Neoadjuvant Chemotherapy for Clinically Node-Positive Breast Cancer
Authors: Matsumoto Akiko , Naruse Saki , Isono Yuka , Maeda Yuka , Sato Ayana , Yamada Miki , Ikeda Tatsuhiko , Jinno Hiromitsu 
Published: March 2023

Abstract
Purpose: Neoadjuvant chemotherapy (NAC) has resulted in the eradication of axillary lymph node metastasis in approximately 40% of patients. Sentinel lymph node biopsy (SLNB) could be an alternative surgical procedure for these patients to avoid complications from axillary lymph node dissection (ALND). However, high false-negative rates of SLNB for clinically node-positive patients were reported in previous prospective trials. The aim of the present study was to evaluate clinicopathological factors and imaging characteristics by MRI and ultrasound (US) as predictors of axillary pathologic complete response (ypN0) after NAC, which enables to identify candidates for SLNB in patients with clinically node-positive disease. Patients and methods: We identified 177 patients with clinically node-positive breast cancer who received NAC from May 2009 to May 2021. All patients underwent MRI and US before and after NAC. Patients were judged to be node-positive when they have the cytologically-proven nodal disease by fine-needle aspiration (FNA) or suspicious lymph nodes by diagnostic imaging. Lymph nodes with the cortical thickness (&gt;3.5mm), loss of fatty hilum, or round shape (short-axis/long-axis ratio &gt; 0.5) were defined as suspicious lymph nodes. To develop a predictive model for ypN0, the association between ypN0 status and clinicopathological and imaging characteristics was assessed by multivariate logistic regression analysis. The area under the receiver operating characteristic (ROC) curve was used to evaluate discrimination by the model. The model was further evaluated in the validation cohort with 20 patients who received NAC from March 2021 to December 2021. Results: The median age was 54.0 (range: 22-79) years and the mean tumor size was 3.97 ±2.29cm. Of 177 patients, 90 (50.8%) patients had luminal, 47 (26.6%) had HER2-positive, and 40 (22.6%) had triple-negative disease. Sequential anthracycline and taxane were administered for 157 (88.7%) patients, and 45 (95.7%) patients with HER2-positive-disease received concomitant anti-HER2 agents preoperatively. Overall, 77 (43.5%) patients achieved ypN0. Independent predictors of ypN0 status were clinical stage N1 (odds ratio [OR]: 9.17 vs. cN2-3, p=0.002), absence of lymphadenopathy after NAC (OR: 8.54, p&lt; 0.001), breast complete response (CR) by MRI (OR: 5.96, p&lt; 0.001), HER2 positivity (OR: 3.80, p=0.008), nuclear grade (NG) 3 (OR: 2.77 vs. NG1-2, P=0.020) and hormone receptor negativity (OR: 2.52, p=0.048). In a model using these predictors, the area under the ROC curve was 0.887 (95% confidence interval: 0.839-0.935, p&lt; 0.001). The sensitivity, specificity, positive predictive value and negative predictive value of the model were 80.0%, 82.8%, 77.9% and 84.5%, respectively. In the validation cohort, the sensitivity, specificity, positive predictive value and negative predictive value were 66.7%, 90.9%, 85.7% and 76.9%, respectively. Among 84 patients who were predicted ypN0 by the model, SLNB was performed in 42 (50.0%) patients, and the identification rate of SLN was 95.2% (40/42). Overall, ALND was omitted in 38 (45.2%) patients and irradiation to regional lymph nodes was performed in 23 (60.5%) out of 38 patients. After a median follow-up of 53.9 months, 5-year recurrence-free survival was comparable between patients with or without ALND (78.0% vs. 94.4%, p=0.259). Conclusions: Our predictive model based on clinicopathological factors and imaging characteristics by MRI and US could help to identify good candidates for the omission of ALND after NAC in patients with clinically node-positive breast cancer.
Citation Format: Akiko Matsumoto, Saki Naruse, Yuka Isono, Yuka Maeda, Ayana Sato, Miki Yamada, Tatsuhiko Ikeda, Hiromitsu Jinno. A Predictive Model for Axillary Pathologic Response after Neoadjuvant Chemotherapy for Clinically Node-Positive Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-01-05.