BackgroundLymph node (LN) metastasis is a relevant predictor for survival in patients with a.o. penile cancer (PeCa), malignant melanoma. The sentinel node (SN) procedure comprises targeted... Show moreBackgroundLymph node (LN) metastasis is a relevant predictor for survival in patients with a.o. penile cancer (PeCa), malignant melanoma. The sentinel node (SN) procedure comprises targeted resection of the first tumour-draining SNs. Here, the hybrid tracer indocyanine green (ICG)-Tc-99m-nanocolloid has been used for several years to combine optical and nuclear detection. Recently, the resource of the nanocolloid precursor stopped production and the precursor was replaced by a different but chemically comparable colloid, nanoscan. Our aim was to study the performance of ICG-Tc-99m-nanoscan compared to ICG-Tc-99m-nanocolloid from a nuclear and surgical perspective.MethodsTwenty-four patients with either PeCa or head-and-neck (H&N) melanoma and scheduled for a SN procedure were included. The initial group (n = 11) received ICG-Tc-99m-nanocolloid until no longer available; the second group (n = 13) received ICG-Tc-99m-nanoscan. Tracer uptake was assessed on lymphoscintigraphy and single-photon emission (SPECT). Intraoperatively, SNs were identified using gamma tracing and fluorescence imaging. Ex vivo (back-table) measurements were conducted to quantify the fluorescence emissions. Chemical analysis was performed to compare the ICG assembly on both precursors.ResultsThe mean tracer uptake in the SNs was similar for ICG-Tc-99m-nanocolloid (2.2 +/- 4.3%ID) and ICG-Tc-99m-nanoscan (1.8 +/- 2.6%ID; p = 0.68). 3 SNs (interquartile range (IQR) 3-4) were detected on lymphoscintigraphy in PeCa patients receiving ICG-Tc-99m-nanoscan compared to 2 SNs (IQR 2-3) in PeCa patients receiving ICG-Tc-99m-nanocolloid (p = 0.045), no differences were observed in H&N patients. Back-table measurements of resected SNs revealed a lower total fluorescence intensity in the ICG-Tc-99m-nanoscan group (24*10(9) arbitrary units (A.U) IQR 1.6*10(9)-14*10(9) in the ICG-Tc-99m-nanocolloid group versus 4.6*10(9) A.U. IQR 2.4*10(9)-42*10(9) in the ICG-Tc-99m-nanoscan group, p = 0.0054). This was consistent with a larger degree of "stacked" ICG observed in the nanoscan formulation. No tracer-related adverse events were reported.ConclusionsBased on this retrospective analysis, we can conclude that ICG-Tc-99m-nanoscan has similar capacity for SN identification as ICG-Tc-99m-nanocolloid and can safely be implemented in SN procedures. Show less
