Multimodal surgical guidance during sentinel node biopsy for melanoma: combined gamma tracing and fluorescence imaging of the sentinel node through use of the hybrid tracer indocyanine green-^99mTc-nanocolloid

Purpose
To evaluate the hybrid approach in a large population of patients with melanoma in the head and neck, on the trunk, or on an extremity who were scheduled for sentinel node (SN) biopsy.

Materials and Methods
This prospective study was approved by the institutional review board. Between March 2010 and March 2013, 104 patients with a melanoma, including 48 women (average age, 54.3 years; range, 18.5-87.4 years) and 56 men (average age, 55.2 years; range, 22.4-77.4 years) (P = .76) were enrolled after obtaining written informed consent. Following intradermal hybrid tracer administration, lymphoscintigraphy and single photon emission computed tomography/computed tomography were performed. Blue dye was intradermally injected prior to the start of the surgical operation (excluding patients with a facial melanoma). Intraoperatively, SN sentinel node s were initially pursued by using gamma tracing followed by fluorescence imaging ( FI fluorescence imaging ) and, when applicable, blue-dye detection. A portable gamma camera was used to confirm SN sentinel node removal. Collected data included number and location of the preoperatively and intraoperatively identified SN sentinel node s and the intraoperative number of SN sentinel node s that were radioactive, fluorescent, and blue. A two-sample test for equality of proportions was performed to evaluate differences in intraoperative SN sentinel node visualization through FI fluorescence imaging and blue-dye detection.

Results
Preoperative imaging revealed 2.4 SN sentinel node s (range, 1-6) per patient. Intraoperatively, 93.8% (286 of 305) of the SN sentinel node s were radioactive, 96.7% (295 of 305) of the SN sentinel node s were fluorescent, while only 61.7% (116 of 188) of the SN sentinel node s stained blue (P < .0001). FI fluorescence imaging was of value for identification of near-injection-site SN sentinel node s (two patients), SN sentinel node s located in complex anatomic areas (head and neck [28 patients]), and SN sentinel node s that failed to accumulate blue dye (19 patients).

Conclusion
The hybrid tracer enables both preoperative SN sentinel node mapping and intraoperative SN sentinel node identification in melanoma patients. In the setup of this study, optical identification of the SN sentinel node s through the fluorescent signature of the hybrid tracer was superior compared with blue dye-based SN sentinel node visualization.