For decades the pathologic nodal status in early breast cancer has been of paramount importance, when evaluating the need for further adjuvant therapies. Nowadays tumor characteristics as receptor status and gene expression essays are increasingly included in this decision process. An increasing number of breast cancer patients are treated with neoadjuvant chemotherapy (NACT). A downstaging of axillary tumor-spread can be achieved in about 40% of the patients receiving NACT. The contribution of NACT to loco-regional tumor control is not fully integrated into the surgical treatment plan. The introduction of sentinel lymph node biopsy (SLNB) and the results of the ACOSOG (American College of Surgeons Oncology Group) Z0011 trial led to a reduction in radicalness of axillary surgery in the adjuvant setting. The impact of NACT on loco-regional tumor control in the neoadjuvant setting has not yet been sufficiently investigated. Moreover the pathologic nodal status after NACT is a strong prognostic marker. Therefore it is most desirable to identify the approximately 40% of patients with pathologic complete response of the axilla and distinguish these patients from those with tumor residuals which might need additional postneoadjuvant treatment. So far attempts to identify these patients via SLNB after NACT have failed to provide acceptable false negative rates (FNR) as reported in the SENTINA (Sentinel-lymph-node biopsy in patients with breast cancer before and after neoadjuvant chemotherapy) trial and ACOSOG Z1071 trial.

Attempts have bee made to further improve FNR of SLNB after NACT in patients with clinically affected lymph nodes at initial presentation. A new concept of surgical axillary staging after NACT is the targeted axillary dissection (TAD). First results have shown to reduce FNR far below the desired threshold of 10%. In this procedure clinically suspicious lymph nodes are evaluated by core needle biopsy (CNB) or fine needle aspiration (FNA) before NACT. A clip is placed into the most suspicious appearing lymph node (target lymph node TLN) directly after biopsy. In case of proven metastasis surgical staging of the axilla is postponed to after completion of NACT. The targeted resection of the clipped node after NACT (target lymph node biopsy TLNB) displays a FNR of 2 - 4.2% according to first results published by Caudle et al. in 2016. In about 3 out of 4 patients the TLN equals a SLN if SLNB is performed simultaneously. The combination of TLNB and SLNB (together so called TAD) seems to further lower FNR. Cases in which tracer uptake in lymph nodes is impaired i.e. by tumor residuals and presumably result in a false negative SLNB can be covered by TLNB.

Clip placement in affected axillary lymph nodes for the purpose of following targeted resection has been implemented into international guidelines. But to date multiple insights into clinical application of TAD are missing. It is not known how often initial CNB/FNA of axillary lymph nodes and following clip placement is successful or has to be abandoned because of technical/medical contraindications. Moreover it is not known how often visualization of the clip after normalization of lymph node structures following NACT and month after initial clip placement is possible. Furthermore information about optimal clip material are lacking. In summary success rates for the targeted resection of the clipped node have to be investigated. Therefore the intraoperative detection rate of the clipped target lymph node is our primary outcome measure.

Patients with clinically affected lymph nodes at initial presentation are planned to be enrolled in multiple german breast centers. In accorndance to german guidelines it is aimed to evaluate the pathologic nodal status via CNB with following clip placement in all of these patients after informed consent. If CNB or clip placement cannot be achieved, technical/medical contraindications are recorded. As the SenTa trial is a registry trial, no strict directives for the further surgical treatment are made. If clip placement is successful, further procedures are left at the investigators choice according to initial pathologic nodal status and potential clinical response to NACT.

If no tumor manifestations are detected in initial CNB, SLNB with simultaneous targeted resection of the clipped node (TLNB) is recommended. The rationale for TLNB in this situation is a FNR of about 20% of initial CNB. On an individual basis upfront ALND can be offered.

If tumor manifestations are detected in initial CNB, targeted resection of the clipped node (TLNB) is strongly recommended because of obvious reasons. If NACT is not planned, upfront ALND should be offered. If patients are planned for NACT further procedures are left at the investigators discretion according to clinical response to NACT. Clinical response after NACT is assessed by axillary ultrasound and an optional needle biopsy if applicable. In case of clinical complete response, TLNB with simultaneous SLNB can be offered on an individual basis.