Factors Associated with Axillary Lymph Node Status in Clinically Node-Negative Breast Cancer Patients Undergoing Neoadjuvant Chemotherapy

SIMPLE SUMMARY: Routine axillary surgery for lymph node staging is necessary for invasive breast cancer, according to current guidelines. However, advances in breast tumor biology and the in vivo tumor response to drugs provided by neoadjuvant chemotherapy (NAC) have led to the development of new effective drugs and higher rates of pathological complete response (pCR) in the breast or axilla. In this retrospective study, we aimed to investigate the factors influencing axillary lymph node (ALN) status after NAC in patients initially diagnosed with clinically node-negative (cN0) breast cancer. We found that pCR of the breast was a predictor of negative ALN status, and the presence of lymphovascular invasion was a predictor of positive ALN status. Our findings support the omission of axillary surgery in patients who achieve breast-pCR and provide the rationale for trials to investigate the feasibility of breast-conserving surgery without concurrent axillary surgery in patients who meet certain criteria. ABSTRACT: Adequate axillary lymph node (ALN) staging is critical for patients with invasive breast cancer. However, neoadjuvant chemotherapy (NAC) was associated with a lower risk of ALN metastasis compared with those who underwent primary surgery among clinically node-negative (cN0) patients. This study aimed to investigate the factors associated with ALN status among patients with cN0 breast cancer undergoing NAC. A total of 222 consecutive patients with cN0 breast cancer undergoing NAC between January 2012 and December 2021 were reviewed. Univariate and multivariate analyses were performed to compare factors associated with positive ALN status. Seventeen patients (7.7%) had ALNs metastases. Here, 90 patients (40.5%) achieved pathologic complete response in the breast (breast-pCR), and all had negative ALN status. Lymphovascular invasion (odds ratio: 29.366, p < 0.0001) was an independent risk predictor of ALN metastasis in all study populations. Among patients without breast-pCR, mastectomies were performed more frequently in patients with ALN metastasis (52.9%) than in those without metastasis (20.9%) (p = 0.013). Our findings support the omission of axillary surgery in patients who achieve breast-pCR. Prospective studies are needed to confirm the feasibility of a future two-stage surgical plan for breast-conserving surgery in patients who are likely to achieve breast-pCR during clinical evaluation.