PURPOSE: Axillary staging is commonly performed in patients with clinically node-positive (cN+) breast cancer undergoing neoadjuvant chemotherapy (NACT), regardless of pathological complete response (pCR). Recent evidence has suggested that ypT0 correlates with ypN0 and favorable prognosis, potentially supporting the omission of axillary staging in such cases. This study aimed to evaluate ypT0 as a predictive factor for ypN status and its prognostic significance in cN+ breast cancer treated with NACT. METHODS: This retrospective study included 302 patients with cN+ breast cancer treated with NACT at Hiroshima University Hospital between 2006 and 2022. Patients were categorized into non-pCR, ypTis, or ypT0 based on ypT status. Associations between breast pCR, ypN status, recurrence-free survival (RFS), and overall survival (OS) were analyzed. RESULTS: Among 302 patients (non-pCR, 74.2%
ypTis, 8.9%
ypT0, 16.9%), the ypN+ rates were 63.3%, 15.2%, and 3.9%, respectively. Logistic regression revealed significant associations among ypT0, ypTis, and ypN0. The five-year RFS and OS rates were 78.6% and 85.2% (non-pCR), 83.8% and 95.5% (ypTis), and 98.0% and 100.0% (ypT0), respectively. Cox regression identified ypT0, but not ypTis, as a significant prognostic factor for both RFS and OS. CONCLUSION: ypT0 status was associated with a low risk of ypN+ and favorable clinical outcomes in cN+ breast cancer, suggesting the potential feasibility of omitting axillary surgery in select patients.