Koos Boeve

76 Chapter 4 In OSCC lymphatic drainage is at least expected in level I-III at the ipsilateral side of the neck [18]. With the second aim to detect unexpected drainage patterns, only 43 patients with previous treatment of the ipsilateral side of the neck were used for lymphatic drainage pattern analysis. In this study, definition of lateralization of the neck is related to the site of the local recurrence or second primary tumour. Ethical consideration Due to the retrospective design no approval was required from the hospital research ethics board of our centers according to the Dutch ethical regulations. SLNB was part of the standard management of these patients and patient information regarding clinical and pathological characteristics and follow-up was retrospectively collected from electronic patient files. RESULTS The data of 53 patients, 29 male (55%) and 24 female (45%) were used for analysis. Mean age was 65 years. Tongue was the most affected tumour location (59%), followed by floor of mouth. Forty-four patients (83%) were diagnosed with a pathologically T1 tumour and 9 patients (17%) with a T2 tumour. These and other characteristics are summarized in Table 1. Characteristics per patient are given in Supplementary data 1. SLNB accuracy Fifty-three patients were used for the SLNB accuracy analysis. Neck dissection, with or without postoperative radiotherapy, was seen most as previous treatment in both the ipsilateral and contralateral neck compared to the local recurrence or second primary side (Table 1). Thirteen patients (25%) died during follow-up of which four (8%) died as a result of the local recurrence or second primary tumour in the oral cavity (disease specific death: median 26 months, IQR 13-42 months). No SLNs were visualized by lymphoscintigraphy in 7 of these 53 patients resulting in an 87% imaging detection rate. In one patient no SLNs were detected intraoperatively, despite preoperative visualization. In two patients with bilateral drainage on lymphoscintigraphy the SLNs were not detected in one neck side intraoperatively, but were harvested in the other side of the neck, resulting in a surgical detection rate of 93% (43/46, Supplementary data 1). In total, at least one SLN was harvested in 85% of the patients (45/53). Three patients had a positive SLN, respectively in the ipsilateral neck with a history of a SLNB, in the