The Role of a Positron- and High-energy Gamma Photon Probe in Intraoperative Localization of Recurrent Melanoma

Purpose: This preliminary study retrospectively evaluated the ability of intraoperative localization of recurrent melanoma using F-18 fluorodeoxyglucose (FDG) and a probe sensitive to both high-energy gamma rays and positrons to enable complete tumor resection and improved patient outcome. Materials and Methods: Three hours before surgery for resection of recurrent melanoma, 5 patients (mean age, 52 ± 22 years) with a history of local surgery, radiation therapy, and/or large habitus received 14.6 ± 3.2 mCi of F-18 FDG. Intraoperative tumor localization was performed with a radiation probe (PET-Probe; IntraMedical Imaging LLC, Los Angeles, CA). Intraoperative tumor tissue activities, background tissue activities, pathology results, and patient follow up (clinical/imaging) were recorded. Results: Eight of the 19 surgical specimens were identified by the probe as having increased FDG uptake when compared with the surrounding tissues before resection. All 8 specimens contained melanoma. Of the 11 specimens that were not identified using the probe, one contained melanoma, yielding a sensitivity of 89% (8 of 9) and a specificity of 100% (10 of 10). In 3 of the 5 cases, the probe allowed the identification of nonvisualized and nonpalpable tumor foci that were later confirmed pathologic. At an average follow up of 210 days (range, 30–515 days), 2 of 5 patients had no evidence of recurrent melanoma by clinical or radiographic evaluations. Conclusion: In the setting of recurrent melanoma, there appear to be potential benefits to intraoperative detection with FDG and a positron-detecting probe, particularly in cases with challenging or altered anatomy.