Page 156 - Sentinel lymph node biopsy in oral cavity cancer - Inne J. den Toom

Chapter 8 They showed a higher pain sensation in the first 3 minutes after injection of [99mTc] Tc-sulfur colloid compared to [99mTc]Tc-tilmanocept. In contrast, in our study a higher pain score was found for [99mTc]Tc-tilmanocept as compared to [99mTc]Tc-nanocolloid, regardless whether [99mTc]Tc-tilmanocept was injected as first or second tracer. However our study size is small and the clinical relevance of a difference of 1 point (median 2.0 vs. 3.0) is questionable. Additionally, Unkart et al. found no statistical differences in breast cancer patients concerning number of hotspots, number of removed SLNs, time to surgical removal or number of blue nodes for [99mTc]Tc-Tilmanocept compared to [99mTc]Tc-sulfur colloid.23 However, this study was not especially designed for analysing differences regarding SLN identification. Randomizing patients for either the one or the other tracer did not clearly clarify discrepancies between both tracers with respect to drainage patterns due to a high variability in lymphatic drainage per patient, especially in complex lymphatic regions. Therefore, it is our opinion that a within-patient study design is superior to reveal characteristics regarding lymphatic drainage patterns of both tracers. As already mentioned in the introduction, [99mTc]Tc-tilmanocept was specifically designed for SLN identification, providing characteristics that could be of potential value in complex lymphatic regions, as is the case in OSCC. Our data clearly underlines its theoretical effect of a more rapid clearance of the radioactivity from the injection site due to its smaller molecular size. This may benefit SLN detection, particularly in situations with close spatial relation between injection site and SLNs, which is especially the case in floor of mouth tumours. Using [99mTc]Tc-tilmanocept, Agrawal et al. supported this theory with an impressively low false-negative rate of 2.56% for SLNB in OSCC, which was also found in FOM tumours.14 In that study however, a complementary neck dissection in the same session was performed as validation method (reference standard) for the SLNB procedure. However, micrometastases remain undetected in up to 15% of routinely processed neck dissection specimens.24,25 Therefore, in case of a negative SLNB, a wait-and-scan approach should be considered as the best gold-standard.26 As a consequence, further studies with long term follow- up are needed to investigate the efficacy of [99mTc]Tc-tilmanocept for detection of occult metastases. In our study, a higher percentage of radioactivity in background was seen for [99mTc] Tc-tilmanocept compared to [99mTc]Tc-nanocolloid. One possible explanation could be the smaller molecular diameter of 7 nanometers, which enhances diffusion into 154