Background: Radar-guided localization (RGL) offers a wire-free, nonradioactive surgical guidance method consisting of a small percutaneously-placed radar reflector and handheld probe. This study investigates the feasibility, timing, and outcomes of RGL for melanoma metastasectomy.
Methods: We retrospectively identified patients at our cancer center who underwent RGL resection of metastatic melanoma between December 2020-June 2023. Data pertaining to patients' melanoma history, management, reflector placement and retrieval, and follow-up was extracted from patient charts and analyzed using descriptive statistics.
Results: Twenty-three RGL cases were performed in patients with stage III-IV locoregional or oligometastatic disease, 10 of whom had reflectors placed prior to neoadjuvant therapy. Procedures included soft tissue nodule removals (8), index lymph node removals (13), and therapeutic lymph node dissections (2). Reflectors were located and retrieved intraoperatively in 96% of cases from a range of 2 to 282 days after placement; the last reflector was not able to be located during surgery via probe or intraoperative ultrasound. One retrieved reflector had migrated from the index lesion, thus overall success rate of reflector and associated index lesion removal was 21 of 23 (91%). All RGL-localized and retrieved index lesions that contained viable tumor (10) had microscopically negative margins. There were no complications attributable to reflector insertion and no unexpected complications of RGL surgery.
Conclusion: In our practice, RGL is a safe and effective surgical localization method for soft tissue and nodal melanoma metastases. The inert nature of the reflector enables implantation prior to neoadjuvant therapy with utility in index lymph node removal.
Keywords: SAVI Scout; adjuvant therapy; cutaneous oncology; melanoma; metastatic melanoma lymph node dissection; neoadjuvant therapy; radar guided reflector; subcutaneous nodule; surgical guidance; tumor localization.
There are a variety of tools available to localize melanoma that had spread to deep layers of the skin or lymph nodes that can guide surgeons to the cancer when the tumor cannot be felt. We evaluated a marker that reflects radar signals that has been studied in breast surgery but not in melanoma. The marker was placed in the tumor before surgery and was located during surgery using a handheld probe, guiding the surgeon to the correct location. An advantage of the radar-reflecting marker we studied is that since it is safe to stay in the body, it can be placed ahead of the use of cancer medications and can keep track of the tumor as it responds to treatment. In a review of 23 surgeries in which the radar-reflecting marker was used, there was one case where the marker migrated away from the tumor and one case where the marker was not able to be located. Monitoring or alternative definitive treatment was provided in each of these cases. Overall, we found the marker to be an effective tumor localization tool for surgeons and safe for patients. Other marker options available are unable or less suitable to be placed a long time in advance of surgery due to either technical or safety reasons, so the radar-reflecting marker is especially useful when it is placed in a tumor ahead of medical treatment leading up to planned surgical treatment.