Sentinel lymph node biopsy (SLNB) is crucial in the management of malignant melanoma treatment and is currently performed by pre-operatively inject a colloid nanomaterial labeled with Technetium (99mTc) as radioactive tracer. Intra-operatively, Patent Blue (PB) will be injected to improve the visualization of the lymphatic tract. However, current pre-operative SLN mapping technique is associated with disadvantages as radiation exposure for both patients and health care staff and logistic challenges, because of time constraints due to short half-live time of 99mTc.

Superparamagnetic iron oxide (SPIO) is a non-radioactive technique using a magnetic tracer (Magtrace® (Endomagnetics Ltd.)) to identify SLNs. Several studies showed that SPIO is non-inferior to dual tracing with 99mTc and PB in breast cancer patients. SPIO is expected to be non-inferior to dual tracing with 99mTc and PB in melanoma patients. However, further research is needed to demonstrate the use of SPIO in pre-operative MRI scanning.

The primary objective of this study is to evaluate the feasibility and diagnostic accuracy of pre-operative MRI scanning using SPIO compared to lymphoscintigraphy (LS) and single-photon emission computed tomography/computed tomography (SPECT/CT) using 99mTc for identifying SLN status in melanoma patients.

Rationale: Sentinel lymph node biopsy (SLNB) is crucial in the management of malignant melanoma treatment and is currently performed by pre-operatively inject a colloid nanomaterial labeled with Technetium (99mTc) as radioactive tracer. Intra-operatively, Patent Blue (PB) will be injected to improve the visualization of the lymphatic tract. However, current pre-operative SLN mapping technique is associated with disadvantages as radiation exposure for both patients and health care staff and logistic challenges, because of time constraints due to short half-live time of 99mTc.

Superparamagnetic iron oxide (SPIO) is a non-radioactive technique using a magnetic tracer (Magtrace® (Endomagnetics Ltd.)) to identify SLNs. Several studies showed that SPIO is non-inferior to dual tracing with 99mTc and PB in breast cancer patients. SPIO is expected to be non-inferior to dual tracing with 99mTc and PB in melanoma patients. However, further research is needed to demonstrate the use of SPIO in pre-operative MRI scanning.

Objective: The primary objective of this study is to evaluate the feasibility and diagnostic accuracy of pre-operative MRI scanning using SPIO compared to lymphoscintigraphy (LS) and single-photon emission computed tomography/computed tomography (SPECT/CT) using 99mTc for identifying SLN status in melanoma patients. A secondary objective is to assess the feasibility and diagnostic accuracy of SPIO/magnetometer (Sentimag®, Endomagnetics Ltd.) in comparison with dual trace gold standard (99mTc and PB) in SLN procedures in melanoma patients.

Study design: A prospective single-arm feasibility study will be performed at the department of Surgical oncology at Zuyderland Medical Center Sittard, the Netherlands.

Study population: Adult patients (≥18 years) with primary melanoma stage I-II and an indication for wide local excision (1 cm) and SLN procedure will be included in the study.

Intervention (if applicable): All patients will undergo lymphatic mapping with a SPIO tracer (Magtrace®), 99mTc and PB.

Main study parameters/endpoints: The concordance in SLN detection rate (sensitivity and specificity) of SPIO/MRI and LS and SPECT/CT using 99mTc.

The concordance in SLN detection rate (sensitivity and specificity) of SPIO/magnetometer and the gold standard dual trace technique using 99mTc/Gamma probe and PB. Additionally, the number of post-injection (skin) reactions, complication and adverse events will be noted.

Inclusion Criteria:

• Patients ≥18 years of age at the time of consent;
• Histological confirmed melanoma (patient must have primary cutaneous melanoma with Breslow thickness ≥ 0.8-2.0mm with or without ulceration or <0.8mm with ulceration (pT1b - pT2b, AJCC 8th edition));
• Indication for wide local excision (margin 1 cm) and SLN procedure;
• Patients should be willing and able to provide informed consent.

Exclusion Criteria:

• Intolerance/hypersensitivity to 99mTc-nanocolloid, PB, iron or dextran compounds;
• Iron overload disease;
• Pregnant or breast-feeding women;
• Previous surrounded lymph node surgery;
• Patients with head and neck melanomas;
• Standard MRI exclusion criteria;
• Implantable (electrical) devices (e.g. pacemaker, cochlear implants, neurostimulator);
• Any other metal implants;
• Claustrophobia;
• MR-incompatible prosthetic heart valves;
• Patients who are unable or refuse to provide informed consent.