Magnetic Technique for Sentinel Lymph Node Biopsy in Melanoma: The MELAMAG Trial

Background: Sentinel lymph node biopsy (SLNB) in melanoma is currently performed using the standard dual technique (radioisotope and blue dye). The magnetic technique is non-radioactive and provides a brown color change in the sentinel lymph node (SLN) through an intradermal injection of a magnetic tracer, and utilizes a handheld magnetometer. The MELAMAG Trial compared the magnetic technique with the standard technique for SLNB in melanoma. Methods: Clinically node-negative patients with primary cutaneous melanoma were recruited from four centers. SLNB was undertaken after intradermal administration of both the standard (blue dye and radioisotope) and magnetic tracers. The SLN identification rate per patient, with the two techniques, was compared. Results: A total of 133 patients were recruited, 129 of which were available for final analysis. The sentinel node identification rate was 97.7 % (126/129) with the standard technique and 95.3 % (123/129) with the magnetic technique [2.3 % difference; 95 % upper confidence limit (CL) 6.4; 5.4 % discordance]. With radioisotope alone, the SLN identification rate was 95.3 % (123/129), as with the magnetic technique (0 % difference; 95 % upper CL 4.5; 7.8 % discordance). The lymph node retrieval rate was 1.99 nodes per patient overall, 1.78 with the standard technique and 1.87 with the magnetic technique. Conclusions: The magnetic technique is feasible for SLNB in melanoma with a high SLN identification rate, but is associated with skin staining. When compared with the standard dual technique, it did not reach our predefined non-inferiority margin.