Koos Boeve

38 Chapter 2 between 1997 and 2008 with a first primary tumour and treated with surgical resection of the tumor at the University Medical Centre Groningen, were selected from our database. Thirty-five patients were excluded because of multiple head and neck tumours (n = 3), irretrievable haematoxylin and eosin (HE) slides (n = 13), or unreliable assessment of infiltration depth because of missing epithelial surfaces and tangential tissue cutting (n = 19), resulting in 211 patients being available for tumour infiltration depth reassessment. Thirty-eight patients (18%) with a pT1 tumour did not undergo a neck dissection, but were followed closely (watchful waiting). This strategy was common in the era before the awareness that an infiltration depth of 4 mm implied a high chance of tumour spread to lymph nodes [6]. The 38 patients - with watchful waiting - had a median tumour infiltration depth of 3.2 mm (IQR 2.1-5.6 mm). In total, 211 patients were used for analysis and 173 of these were treated with neck dissection. The clinical and histopathological characteristics of the study group are shown in Table 1. In total, 72 patients received postoperative radiotherapy, but none of the watchful waiting patients were postoperatively irradiated. The median follow-up time was 64 months (range 0-193 months). Thirteen patients (6%) were diagnosed with local recurrence and 26 (12%) with regional recurrence. Of the 38 watchful waiting patients, two patients were diagnosed with a local recurrence and seven patients with regional recurrences during their follow-up. Sixty-eight patients (32%) died in the first 5 years after treatment, 57% because of the OSCC. OSCC related death (median 63 years; IQR 54-70 years) occurred at a significantly younger age than OSCC unrelated death (median 71 years; IQR 62-79) (p = 0.010). Data collection Clinical and pathological data were collected retrospectively from the patient files. Tumour H&E-stained slides were revised by one dedicated head and neck pathologist, and tumour infiltration depth was reassessed by the use of digital microscopy and computerised measurements (Research Assistant 6; RVC; Soest, The Netherlands). Tumour infiltration depth was measured from the mucosal surface or from the reconstructed mucosal surface in cases of ulcerated or exophytic tumours [7], this differs from the AJCC manual in using the mucosal surface instead of the mucosal basement membrane [2]. ENE was defined as an extension of tumour cells beyond the nodal capsule and forms part of the standard pathology report in our centre. Cases with no convincing extension beyond the nodal capsule (i.e. no stromal reaction) were scored as negative. We revised the pathological tumour and pathological nodal classification according to the 8 th edition. Five-year disease specific survival (DSS) was defined as the time from first treatment until disease specific death or the last follow-up, with a maximum of 5-years. Three-year disease-free survival