Sentinel lymph node (SLN) status is pivotal for treatment decisions in breast cancer patients. The dual technique with Technetium99m (Tc99) and blue dye (BD) is yet the current routine for SLN detection. However, the same reliability has been presented by superparamagnetic iron oxide nanoparticles (SPIO). The aim of this study was to determine if SLN detection using ultra-low dose SPIO is feasible.

Sentinel lymph node (SLN) status is pivotal for treatment decisions in breast cancer patients. The dual technique with Technetium99m (Tc99) and blue dye (BD) is yet the current routine for SLN detection. However, the same reliability has been presented by superparamagnetic iron oxide nanoparticles (SPIO). The aim of this study was to determine if SLN detection using ultra-low dose SPIO is feasible.

This is a phase Ib/II interventional dose-escalation single arm study. There will be a dose escalation of SPIO (0.1ml, 0.25ml and 0.5 ml) with a minimum of 5 patients per step. If 4 or more procedures are successful, no further dose escalation will be performed. 30 patients will be included with the minimal successful dose.

Furthermore, a total of 20 patients with the minimal successful dose will be included for the secondary objective A - to evaluate if it is possible to map and stage sentinel lymph nodes with SPIO-enhanced axillary MRI. For the secondary objective B - an additional of 20 patients with the minimal successful dose will be included to evaluate if SPIO in a low dose creates any SPIO related artifacts on breast MRI after breast conserving surgery. These two parts of the study are optional, and the patients will be asked specifically about participation in these two objectives, A and B. All included patients will be evaluated for skin staining at study visits.

Inclusion Criteria:

1. Female aged above 18 years
2. Signed and dated written informed consent before the start of specific protocol procedures
3. Histologically confirmed breast cancer planned for breast conserving surgery and sentinel lymph node biopsy

Exclusion Criteria:

1. Pregnant or breast-feeding
2. Iron overload disease
3. Known hypersensitivity to iron, dextran compounds or blue dye.
4. Inability to understand given information and give informed consent or undergo study procedures
5. MRI (subgroup of patients): Conditions contraindicating MRI including, but not limited to, BMI > 40 kg/m2, claustrophobia, metallic implants or internal electrical devices (e.g., pacemaker) and permanent makeup or tattoos which in the Investigator's opinion might jeopardise the patient's safety or imaging.