Chemotherapy in clinically node positive breast cancer patients is increasingly administrated in a neoadjuvant setting. The standard treatment regimen in these cases is then: neoadjuvant chemotherapy (NAC) followed by breast surgery and an axillary lymph node dissection (ALND). NAC results in axillary pathologic complete response (pCR) in 1 out of 3 patients, indicating a complete absence of axillary metastases after completion of NAC. In such events, ALND can be regarded as overtreatment that creates unnecessary morbidity. Less invasive axillary surgery which can accurately assess axillary pCR is therefore preferred over standard ALND in all patients. In case of detection of remaining axillary lymph node metastases by this less invasive axillary surgical procedure, completion axillary treatment is standard of care.

The novel RISAS procedure is introduced as a possible less invasive axillary staging procedure. RISAS procedure contains Radioactive Iodine Seed localisation in the Axilla in axillary node positive breast cancer combined with a Sentinel node procedure. The iodine seed in the axillary lymph node metastasis will be placed prior to start of NAC.

Inclusion Criteria:

• Female patient with pathologically confirmed axillary lymph node positive invasive primary breast cancer, treated with neoadjuvant chemotherapy
• Willing and able to undergo all study procedures.
• Has personally provided written informed consent.

Exclusion Criteria:

• Age < 18
• Pregnancy or lactation
• Contra indications for undergoing iodine seed placement or sentinel lymph node biopsy, such as allergic reaction on iodine, 99m Technetium or patent blue.
• Recurrent breast cancer
• Previous axillary surgery or radiotherapy
• Patients with periclavicular lymph node metastases (cN3)
• Patients with advanced breast cancer (i.e. patients with distant metastases, treated without any furter surgical procedures)