Sentinel lymph node biopsy (SLNB) is a diagnostic staging procedure that aims to identify the first draining lymph node(s) from the primary tumor, the sentinel lymph nodes (SLN), as their histopathological status reflects the histopathological status of the rest of the nodal basin. The routine SLNB procedure consists of peritumoral injections with a technetium-99m [99mTc]-labelled radiotracer followed by lymphoscintigraphy and SPECT-CT imaging. Based on these imaging results, the identified SLNs are marked for surgical extirpation and are subjected to histopathological assessment. The routine SLNB procedure has proven to reliably stage the clinically negative neck in early-stage oral squamous cell carcinoma (OSCC). However, an infamous limitation arises in situations where SLNs are located in close vicinity of the tracer injection site. In these cases, the hotspot of the injection site can hide adjacent SLNs and hamper the discrimination between tracer injection site and SLNs (shine-through phenomenon). Therefore, technical developments are needed to bring the diagnostic accuracy of SLNB for early-stage OSCC to a higher level. This review evaluates novel SLNB imaging techniques for early-stage OSCC: MR lymphography, CT lymphography, PET lymphoscintigraphy and contrast-enhanced lymphosonography. Furthermore, their reported diagnostic accuracy is described and their relative merits, disadvantages and potential applications are outlined.
Purpose Sentinel lymph node (SLN) biopsy has proven to reliably stage the clinically negative neck in early-stage oral squamous cell carcinoma (OSCC). [99mTc]Tc-tilmanocept may be of benefit in OSCC with complex lymphatic drainage patterns and close spatial relation to SLNs. Methods A prospective within-patient evaluation study was designed to compare [99mTc]Tc-tilmanocept with [99mTc]Tc-nanocolloid for SLN detection. A total of 20 patients with early-stage OSCC were included, who underwent lymphoscintigraphy with both tracers. Both lymphoscintigraphic images of each patient were evaluated for SLN detection and radiotracer distribution at 2–4 h post-injection. Results The injection site’s remaining radioactivity was significantly lower for [99mTc]Tc-tilmanocept (29.9%), compared with [99mTc]Tc-nanocolloid (60.9%; p < 0.001). Radioactive uptake in SLNs was significantly lower for [99mTc]Tc-tilmanocept (1.95%) compared with [99mTc]Tc-nanocolloid (3.16%; p = 0.010). No significant difference was seen in SLN to injection site ratio in radioactivity between [99mTc]Tc-tilmanocept (0.066) and [99mTc]Tc-nanocolloid (0.054; p = 0.232). A median of 3.0 and 2.5 SLNs were identified with [99mTc]Tc-tilmanocept and [99mTc]Tc-nanocolloid, respectively (p = 0.297). Radioactive uptake in higher echelon nodes was not significantly different between [99mTc]Tc-tilmanocept (0.57%) and [99mTc]Tc-nanocolloid (0.86%) (p = 0.052). A median of 2.0 and 2.5 higher echelon nodes was identified with [99mTc]Tc-tilmanocept and [99mTc]Tc-nanocolloid, respectively (p = 0.083). Conclusion [99mTc]Tc-tilmanocept had a higher injection site clearance, but at the same time a lower uptake in the SLN, resulting in an SLN to injection site ratio, which was not significantly different from [99mTc]Tc-nanocolloid. The relatively low-radioactive uptake in SLNs of [99mTc]Tc-tilmanocept may limit intraoperative detection of SLNs, but can be overcome by a higher injection dose.
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