Refining the sentinel node procedure Clinical implementation of a multimodal approach for minimally invasive staging of tumors with inguinal lymphatic drainage

Introduction: Preoperative sentinel node mapping is routinely performed with lymphoscintigraphy, after injection of a radio-colloid. Intraoperatively, sentinel nodes are conventionally pursued with a gamma ray detection probe and a blue dye. The aim of this study was to evaluate the added value of intraoperative fluorescence imaging to the radioguided procedure for sentinel nodes located in the groin. For this, the hybrid tracer ICG-99mTc nanocol-loid was used, which is both radioactive and fluorescent. Additionally, the feasibility and accuracy of surgical navigation based on preoperatively acquired SPECT/CT images combined with this hybrid tracer was stu-died. Material and methods: Thirty patients scheduled for an inguinal sentinel node procedure were included in this study. After peritumo-ral injection of ICG- 99mTc nanocolloid, lymphoscinitigraphy and SPECT/CT images were obtained. During surgery, a combination of gamma tracing with a handheld gamma probe and a portable gamma camera to-gether with fluorescence guidance using a fluorescence camera was used to harvest the sentinel nodes. Ad-ditionally, in 10 patients navigation of the handheld gamma probe to the sentinel nodes based on 3D SPECT/CT images was performed prior to incision in order to evaluate the navigation accuracy. Results: Preoperatively, SPECT/CT was able to identify 18 additional sentinel nodes, next to the ... detected sentinel nodes by lymphoscintigraphy. In total, 104 sentinel nodes were excised during surgery, of which merely 55,8% had stained blue and 98% were detected with fluorescence in vivo. In 10 patients, surgical navigation was used during the procedure and the mean error compared with the location indicated by the gamma probe was 5.4 mm. Conclusion: Inguinal sentinel node bipsy using the hybrid tracer ICG-99mTc nanocolloid is feasible in and ishowed to have a superior detectability rate compared to the conventionally used blue dye. ICG- 99mTc nanocolloid enables the combination of unaltered preoperative sentinel node identification using lymphoscintigraphy and SPECT/CT with an improved bimodal (radioactive and fluorescent) signal for intraoperative sentinel node de-tection. Surgical navigation based on SPECT/CT data combined with this hybrid tracer is feasible and offers a promising perspective for improving the sentinel node procedure in areas of complex and deep lymphatic drainage.