Koos Boeve

75 SLNB in oral cancer after previous neck treatment of the neck with SLNB, neck dissection, (chemo)radiotherapy or a combination of these modalities (Supplementary data 1). Twelve patients were previously included in the study by Flach et al., their follow-up was updated [5]. The SLNB procedure was described extensively before [16,17]. Briefly, patients received preoperatively injections with 99m Tc-nannocolloid followed by dynamic and static lymphoscintigraphy and SPECT-CT scanning one day before surgery, intra-operatively gamma probe detection and postoperative step serial sectioning of the sentinel lymph node with additional immunohistochemical keratin staining. As visualized in our study design (Figure 1) all 53 patients were used for analysis regarding the accuracy of the procedure and 43 patients were included for the drainage pattern analysis. Earlier studies showed the potential of bilateral drainage patterns in well-lateralized patients. Because of this potential bilateral drainage also 10 patients were included with a history of only contralateral treatment of the neck (their first tumour was contralateral of the second) whom might affect the SLNB accuracy [16,18]. 53 OSCC patients Inclusion: · cT1-2N0 second primary · Resection with SLNB procedure · Previously treated neck 43 OSCC patients Second primary at the treated side of the neck 10 OSCC patients Second primary at the untreated side of the neck SLNB accuracy analysis Lymphatic drainage pattern analysis Figure 1: Study design. All 53 patients were used for the SLNB accuracy analysis, only the 43 patients with a history of neck treatment at the ipsi- or bilateral side were used for the analysis of altered lymphatic drainage patterns.