Koos Boeve

178 Chapter 9 retrospectively analysed the sensitivity and NPV of the SLNB in a well-defined cohort using watchful waiting as reference standard for the SLNB negative neck and SPECT-CT scanning and step-serial-sectioning with additional keratin staining were part of the protocol. We confirmed the high sensitivity (85%) and NPV (94%) for the detection of occult metastasis in early stage OSCC [11]. Randomized studies which compare the accuracy of the SLNB procedure and END procedures for detecting occult metastasis in OSCC patients with a clinically negative neck (cN0) are not available yet [12]. However, the reported regional recurrence rate in the pN0 staged neck is 6% in a meta-analysis of the SLNB procedure [1] and comparable to the regional recurrence rate in END studies which is reported between 3% to 10% [12-14]. Thus, the SLNB procedure has an accuracy in the detection of occult metastasis in early stage OSCC at least as high as the END procedure with a lower complication and postoperative morbidity rate. In 2018, a conference about the SLNB in head and neck cancer was held in London with the aim to reach consensus about the SLNB procedure [15,16]. After that conference, consensus about imaging protocols [15] and surgical procedures were [16] reported and a report about the pathological consensus is expected soon. Neck staging with the SLNB can be used in patients with a clinically negative neck based on preoperative imaging using Computed Tomography (CT), Magnetic Resonance Imaging (MRI) or ultrasound with or without fine needle cytology aspiration (USgFNAC) [15,16]. In a review the sensitivity and specificity of these imaging modalities for the detection of occult metastasis in cN0 patients was reported (reviewed in [17]). Although five studies reported high specificities (92- 100%) for CT, US and USgFNAC, these modalities lack sufficiently high sensitivities in cN0 OSCC patients: CT 49-60%, MRI 55-65%, US 48-66% and USgFNAC 73% [18-21] and should therefore always be followed by a SLNB procedure. Consensus about the preoperative SLNB imaging protocol consisted of two to four mucosal injections peritumourally of the tracer ( 99m TC-labelled nanocolloids). The injection activity depends on the one (40-50 MBq) or a two day (70-120 MBq) protocol and should be diluted in a maximum volume of 0.4 to 0.5 mL [15]. The injection is immediately followed by dynamic (0-10 min) lymphoscintigraphy and later on by early static (15 min) and late static (2 hrs) lymphoscintigraphy [15]. The lymphoscintigraphy should be followed by SPECT-CT (>2 hrs) [15]. The use of both the SPECT-CT and the lymphoscintigraphy resulted in the additional detection of SLNs in 22% of the cases in a study with 66 SLNB patients [22]. Moreover, in 8% of the cases were non-sentinel lymph nodes reported as SLNs by using planar lymphoscintigraphy only. A hand-held gamma probe is recommended for the intra- operative detection [15,23].