Evaluation of mobile gamma camera imaging in sentinel lymph node biopsy for melanoma independent of pre-operative lymphscintigraphy.

Abstract

e19062 Background: Sentinel lymph node biopsy (SLNB) is the standard method for staging cutaneous melanoma and involves identifying the first node(s) draining a tumor, by detecting an intradermally-injected radioactive colloid tracer. Intra-operatively the sentinel node(s) are identified with a hand-held gamma probe. Pre-operative lymphoscintigraphy is obtained to identify draining lymph node basins, but requires coordinating schedules between nuclear medicine and the operating room. A pilot study utilizing Mobile Gamma Camera (MGC) devices in conjunction with conventional lymphoscintigraphy for intraoperative sentinel node localization provided clinical benefit in 20% of patients. However, utilizing MGC devices to localize lymph node basins at the time of surgery independent of conventional lymphoscintigraphy with a fixed gamma camera (FGC) has not been adequately studied. Here, we present the results of a clinical trial utilizing MGC devices to localize lymph node basins in a manner blinded to the FGC images in order to compare the modalities directly. Methods: In 2011-12 18 patients underwent Tc99 sulfur colloid lymphoscintigraphy, and MGC survey immediately pre-operative by the study surgeon. The study surgeon established an operative plan using the MGC survey, while blinded to lymphoscintigraphy results. SLNB was then performed with use of a gamma probe and intra-operative MGC imaging. Results: 22 lymph node basins were detected in 18 imaged patients by lymphoscintigraphy. All of these basins were identified by the study surgeon using the MGC device in the pre-operative setting prior to un-blinding. In every case the operative plan established based on pre-operative MGC imaging was confirmed by the FGC images. In two cases, additional information from the MGC images aided surgical decision-making. 5 of 22 lymph node basins were positive for metastasis. All of these basins were identified by pre-operative MGC imaging, and all individual positive nodes were identified by intra-operative MGC imaging. Conclusions: Pre-operative MGC imaging in sentinel lymph node biopsy can provide comparable information for operative planning, compared to standard FGC imaging.