The investigator developed this protocol to accurately assess lymph node response to neoadjuvant chemotherapy in clinical stage N1 (cN1) breast cancer patients. Accuracy of sentinel lymph node biopsy (SLNB) alone and in combination with the removal of wire-localized-clip-marked nodes will be analyzed. New model to predict lymph node pathological complete remission (pCR) so as to safely avoid axillary lymph node dissection in cN1 breast cancer patients is sought for.

The investigator developed this protocol to accurately assess lymph node response to neoadjuvant chemotherapy in cN1 breast cancer patients. In brief, pathologically proven positive axillary lymph node will be clip-marked before the initiation of neoadjuvant chemotherapy (NACT) and continuously monitored through out the course of chemotherapy with ultrasound. After the completion of neoadjuvant chemotherapy, a wire will be placed to localize the clip-marked node before surgery. During surgery, a standard sentinel lymph node biopsy will be performed as well as the removal of the wire localized node. Axillary lymph node dissection (ALND) will be performed in all participants. Accuracy of SLNB alone and in combination with the removal of wire-localized-clip-marked nodes will be analyzed. Axillary ultrasound and CT scan will be performed before and after neoadjuvant chemotherapy for all patients enrolled. By assessing clinical-pathological and imaging data acquired from this trial, the investigator look forward to developing a model to accurately predict lymph node pCR (AUC >0.85) so as to safely avoid axillary lymph node dissection in cN1 breast cancer patients.

Inclusion Criteria:

• between the age of 18 and 65
• Eastern Cooperative Oncology Group (ECOG) score 0 or 1
• pathologically proven positive axillary lymph node
• enough renal and liver function to sustain chemotherapy
• informed consent obtained

Exclusion Criteria:

• inflammatory breast cancer
• being pregnant or nursing
• neoadjuvant chemotherapy not planned