The Use of Radar-Guided Localization to Identify Metastatic Melanoma After Neoadjuvant Immunotherapy

Radar-guided localization (RGL) is a nonradioactive, wireless technique used to localize target lesions for resection via a percutaneously placed intra-tumoral reflector and a handheld probe intraoperatively. RGL plays a critical role in the setting of nonpalpable lesions. This study describes RGL for patients undergoing neoadjuvant immunotherapy (NEO) for metastatic melanoma.

A retrospective review included stage III-IV melanoma patients who underwent NEO followed by metastasectomy with RGL.

Twenty-three patients were identified. Median age was 65 years; ten were female. Twenty patients had a radiographic response to NEO in the target lesion, and three demonstrated progression on NEO. Fourteen lesions were palpable prior to NEO, and five (36%) remained palpable after NEO. Reflectors were successfully retrieved in all 23 patients at a median of 99 (range 1-282) days after RGL placement. Operations included 18 targeted index lymph node dissections, two complete therapeutic lymph node dissections, and three subcutaneous/soft tissue nodule resections. Nineteen patients had a major pathologic response to NEO (0 to <10% viable tumor), one patient had a partial response (10-50% viable tumor), and three patients had a pathologic nonresponse (>50% viable tumor).

In this series of RGL and resection of metastatic melanoma after NEO, two-thirds of the index lesions became nonpalpable after NEO, and RGL allowed for accurate intraoperative identification and retrieval at any interval (days to months). Specific target lesion marking with fiducial markers for intraoperative identification and targeted resection allows the treating team to examine pathologic response and dictate further therapy on an individualized basis.