From cN2 to ypN0: Nodal Downstaging After Neoadjuvant Treatment in Breast Cancer-A Retrospective Cohort Study from a Tertiary Cancer Center

Background/Objectives: In patients with clinically node-positive breast cancer, axillary response to neoadjuvant systemic treatment is heterogeneous and might depend on tumor biology. In patients with cN2 disease, the identification of factors linked to nodal response could improve risk stratification and contribute to the development of individualized post-neoadjuvant axillary management strategies.

Methods

This cohort study has a retrospective design and included 560 female patients with invasive breast cancer (proven via biopsy) and cN2 disease. All patients received neoadjuvant systemic treatment accompanied by breast and axillary surgery at the Institute of Oncology "Prof. Dr. Ion Chiricuță" Cluj-Napoca (IOCN), Romania, between 2017 and 2025. The primary endpoint was the rate of axillary pathological complete response (pCR) following neoadjuvant systemic therapy, defined as ypN0. Secondary endpoints included breast pCR (ypT0), overall pCR (ypT0N0), the association between breast and axillary pathological response and survival analysis, including overall survival (OS) and disease-free survival (DFS). Clinicopathological predictors were assessed using univariate and multivariate logistic regression, while survival outcomes were evaluated with time-to-event analyses.