Koos Boeve

65 SLNB in early oral cancer neck SLNB studies [15]. Moreover, the ITC, micro- and macrometastasis ratio is comparable with other studies, indicating that we did not miss ITCs using this protocol. We therefore assume that this protocol has not influenced our results. However, we propose to continue SSS and classification of SLN metastasis size according to Hermanek, until well powered studies have defined the clinical impact of the SLN metastasis size [18]. Afterwards, further research is needed to reach consensus about minimal interval thickness for SSS to detect these metastases with clinical impact. Thirty-three patients had SLNs on both sides of the neck, also in cases with lateralised border of tongue tumours. Moreover, 1 patient did not show ipsilateral lymphatic drainage patterns, but instead showed a negative contralateral SLN. This patient did not develop IRR at either side within 34 months follow-up. These 34 (37%) patients showed the advantage of detecting unexpected drainage patterns with the SLNB procedure and were thereby prevented from undertreatment. Despite the good accuracy of the SLNB procedure, improvements might be made for the clinical negative neck. For example, in our centres the use of blue dye has been abandoned, because it blurred surgical tumour resection margins intra-operatively. A disadvantage of the SLNB procedure is the second operation for the MRND after a positive SLNB. Especially in frail elderly or patients with multiple comorbidities, a second operation with general anaesthesia is undesirable due to a higher complication andmortality chance [34]. Moreover in all positive cases, scar tissue makes the neck dissection surgery more challenging in the SLN levels. To avoid repeat surgery, the possibility of intraoperatively staging of SLNs with frozen sections has been studied [35]. However, frozen sections have a substantial false negative rate; therefore frozen sections of the SLNs are not applied in our centres. Also a substantial amount of the SLN is lost for the FFPE sections and thereby increasing the risk of missing ITCs and micrometastases [35]. In an ideal situation, patients at high risk of lymph node metastases are preoperatively selected for MRND or watchful waiting. In the current study, an infiltrative tumour border configuration or a pT2 tumour was significantly associated with more regional metastases. Our research group reported earlier infiltration depth and lymphovascular invasion as independent predictors for nodal status in pT1-2N0 and N-status determination by routine HKD and watchful waiting [20]. These markers are not associated with positive lymph nodes in this study. The lack of significance could be explained by the difference in patient selection between the mentioned study by Melchers (cN0 and cN+) and this study (cN0) [20]. Therefore, the SLNB procedure is still more accurate in detecting occult metastasis in