Delayed SLND for Patients With Breast Cancer Undergoing Primary Systemic Treatment

All patients will receive Radioisotope according to standard of care. They will also receive SPIO in a timeframe of clinical convenience, depending on whether primary response is planned by means of MRI. For patients that are ycN0, SLND or TAD will be performed. For those that convert from cN1 to ycN0, the index lymph node will be marked with a paramagnetic marker. Axillary surgery will be undertaken with the magnetic technique and each retrieved lymph node will be controlled for radiation. Upon the completion of the procedure, a background control will be performed with the radioactive signal as guide, to ensure standard of care best practice. Any palpable lymph nodes that are not sentinels with either tracer may be removed at surgeon discretion but will be reported seperately.