Magnetic seed localization in patients with nodal stage III melanoma and neoadjuvant immunotherapy, a feasibility study

Abstract Introduction Current guidelines for resectable macroscopic stage III melanoma recommend neoadjuvant immunotherapy and therapeutic lymph node dissection (TLND), followed by adjuvant treatment. However, the PRADO trial showed that TLND and adjuvant treatment could be omitted in patients with a major pathological response (MPR) in the index node after neoadjuvant immunotherapy. This questions whether TLND is necessary in patients with MPR after index node resection (INR). The aim of this study was to evaluate the feasibility of using a magnetic seed (Magseed®) to localize the index node for selective removal in patients with stage III melanoma receiving neoadjuvant immunotherapy. Method From November 1, 2024, consecutive patients with resectable stage III melanoma and planned TLND after neoadjuvant immunotherapy were enrolled. Prior to treatment, a Magseed® was placed in the largest metastatic node under ultrasound guidance. INR was performed concurrently with TLND, 6–8 weeks after therapy initiation. Before skin incision, a handheld magnetometer (Sentimag®) was used to localise the marker before incision. The index node was analysed separately for pathological response and seed presence. Result Twelve of the planned 20 patients have undergone surgery so far. Preliminary data show successful transcutaneous localization and retrieval of the marked node in 11 of 11 patients (100%) with femoral or axillary lymph node metastases. The study is ongoing and actively recruiting patients. Discussion In this first feasibility trial using Magseed® as a marker for INR in patients with stage III melanoma, preliminary data supports the feasibility of this approach.