Prognostic value of pathological nodal burden after neoadjuvant chemotherapy in initially cN0-1 breast cancer patients: a dual-center, 10-year survival analysis.

Background: There is an interest in performing de-escalating axillary surgery after neoadjuvant chemotherapy (NAC). However, the significance of residual axillary node disease after NAC has not been well studied.

Objectives: To investigate the pathological residual axillary lymph node tumor burden (ypN) of patients with initial clinical nodal stage cN0-1 breast cancer after NAC and determine its prognostic value.

Design: Initial cN0-1 breast cancer patients who received NAC followed by axillary surgery at the First Hospital of Jilin University and the First Affiliated Hospital of Xi'an Jiaotong University between January 2011 and December 2019 were included.

Methods: Survival outcomes were compared according to different clinical and pathological stage and nodal response to NAC. The main outcomes were disease-free survival (DFS) and overall survival (OS). Factors associated with survival were defined by Cox regression analysis.

Results: A total of 911 patients were included, among whom 260 had cN0 and 651 had cN1 tumors. After NAC, 410 patients were ypN0, and another 501 were ypN+. The median follow-up time was 63 months. There was no significant difference in DFS or OS between the cN0 and cN1 groups in hormone receptor positive (HR+)/human epidermal growth factor receptor 2 positive (HER2+) and HR-/HER2- subtypes; instead, ypN status was significantly related to DFS and OS. In HR+/HER2- subtype, both cN and ypN stages did not show significant survival differences, but the ypN number and the nodal response to NAC showed significant prognostic value ( < 0.05). Among HR-/HER2+ patients, all cN status, ypN status, ypN number, and nodal response were significantly associated with survival ( < 0.05). Furthermore, tumor biology, axillary surgery, ypN status, pathological tumor size, and radiotherapy were independent prognostic factors for DFS and OS.

Conclusion: The ypN status after NAC provide more prognostic information than the initial cN stage in cN0-1 patients, and the surgical axillary staging after NAC may have high clinical value.