A Hybrid Radioactive and Fluorescent Tracer for Sentinel Node Biopsy in Penile Carcinoma as a Potential Replacement for Blue Dye

Background: Sentinel node (SN) biopsy in penile cancer is typically performed using a combination of radiocolloid and blue dye. Recently, the hybrid radioactive and fluorescent tracer indocyanine green (ICG)-Tc-99m-nanocolloid was developed to combine the beneficial properties of both radio-guidance and fluorescence imaging. Objective: To explore the added value of SN biopsy using ICG-Tc-99m-nanocolloid in patients with penile carcinoma. Design, setting, and participants: Sixty-five patients with penile squamous cell carcinoma were prospectively included (January 2011 to December 2012). Preoperative SN mapping was performed using lymphoscintigraphy and single-proton emission computed tomography supplemented with computed tomography (SPECT/CT) after peritumoural injection of ICG-Tc-99m-nanocolloid. During surgery, SNs were initially approached using a gamma probe, followed by patent blue dye and/or fluorescence imaging. A portable gamma camera was used to confirm excision of all SNs. Surgical procedure: Patients underwent SN biopsy of the cN0 groin and treatment of the primary tumour. Outcome measurements and statistical analysis: The number and location of preoperatively identified SNs were documented. Intraoperative SN identification rates using radio- and/or fluorescence guidance were assessed and compared with blue dye. Statistical evaluationwas performed using a two-sample test for equality of proportions with continuity correction. Results and limitations: Preoperative imaging after injection of ICG-Tc-99m-nanocolloid enabled SN identification in all patients (a total of 183 SNs dispersed over 119 groins). Intraoperatively, all SNs identified by preoperative SN mapping were localised using combined radio-, fluorescence-, and blue dye guidance. Fluorescence imaging enabled visualisation of 96.8% of SNs, while only 55.7% was stained by blue dye (p < 0.0001). The tissue penetration of the fluorescent signal, and the rapid flow of blue dye limited the detection sensitivity. A tumour-positive SN was found in seven patients. Conclusions: ICG-Tc-99m-nanocolloid allows for both preoperative SN mapping and combined radio- and fluorescence-guided SN biopsy in penile carcinoma patients and significantly improves optical SN detection compared with blue dye. (C) 2013 European Association of Urology. Published by Elsevier B.V. All rights reserved.