Exploring an Alternative Preoperative Sentinel Lymph Node Mapping Method Using a Magnetic Tracer and Magnetic Resonance Imaging for Melanoma Patients: SCARLETT Study Protocol.

introductionSentinel lymph node biopsy (SLNB) plays a critical role in the clinical management of malignant melanoma. The current standard of care involves the preoperative injection of a Technetium-labeled (99mTc) colloidal nanomaterial to facilitate lymphatic mapping. During surgery, patent blue (PB) is administered to enhance visualization of the lymphatic pathways. However, this dual-tracer approach presents notable drawbacks, including patient exposure to ionizing radiation and logistical challenges stemming from the short half-life of (99mTc). Superparamagnetic iron oxide nanoparticles (SPIO) have emerged as a nonradioactive alternative. Used in conjunction with a handheld magnetometer system (Magtrace® and Sentimag®, Endomagnetics Ltd.), SPIO enables SLN detection without the need for nuclear medicine infrastructure. In clinical studies involving breast cancer patients, SPIO has demonstrated non-inferiority to the conventional 99mTc and PB protocol. Given these findings, SPIO is hypothesized to offer equivalent performance in melanoma patients. This study is designed to evaluate the non-inferiority of preoperative magnetic resonance imaging (MRI) using SPIO compared to traditional lymphoscintigraphy and single-photon emission computed tomography/computed tomography with 99mTc for SLN identification in melanoma. Additionally, the study assesses the non-inferiority of intraoperative SLNB using SPIO and the Sentimag® device relative to the current gold standard based on 99mTc.

methodsA prospective, single-arm, non-inferiority study will be conducted at the Department of Surgical Oncology, Zuyderland Medical Center, Sittard, the Netherlands. The study will enroll 140 adult patients diagnosed with stage I-II primary melanoma who are scheduled to undergo wide local excision and SLNB. All participants will undergo lymphatic mapping using both Magtrace® and 99mTc. The MRI protocol, previously evaluated in a pilot study, was demonstrated to be feasible. Implementation of the MRI protocol will proceed if non-inferiority is established within a predefined margin of 5%.

conclusionElimination of radiation exposure is beneficial for both patients and healthcare personnel. Moreover, logistic challenges will be eliminated as SPIO can be injected several days before surgery, immediately followed by MRI scanning. Scheduled surgeries will not be jeopardized by preoperative logistics and procedures. It will increase hospital-oriented productivity, patient-friendliness and comfort as surgical delays are avoided.