Koos Boeve

12 Chapter 1 Histopathological assessment of the tumour resection specimen enables patient selection for adjuvant treatment in cases with unfavourable pathological features. Surgery is often followed by radiotherapy in patients with an intermediate risk for recurrences defined as lymphovascular or perineural invasion, close surgical resection margins (1-5 mm), pT3-T4 staged tumours or a ≥pN1 lymph node status [14,15]. Postoperative radiotherapy is combined with chemotherapy in cases with a high risk for local, regional or distant recurrence what is defined as positive surgical resection margins (less than 1 mm tumour free margin), multiple positive lymph nodes or extranodal extension [14,15]. Surgical re- resection is an option in cases with close or positive tumour resection margins for local control with curative intent. Despite surgical resection and adjuvant therapy based on the pathological features, curative treatment is still a challenge and reflected in the overall survival (OS) that only improved six percent in the Netherlands from 56% in 1989 to a 62% five-year OS in 2012 for OSCC in general [11,16]. Two important challenges affecting the survival in OSCC are studied in this thesis: first, the detection of occult metastasis using the sentinel lymph node biopsy or molecular tumour biomarkers in early stage OSCC. And secondly, the detection of local recurrences and second primary tumours using molecular tumour biomarkers in saliva. A B paranasal sinuses nasal cavity nasopharynx 1B oral cavity oropharynx pharynx hypopharynx 111 VI epiglottis salivary glands supraglottis IV glottis larynx subglottis Figure 1. Head and neck locations. The main anatomical locations of head and neck cancer (1A) and the six cervical neck levels with four sublevels (1B). Oral cavity tumours metastasize mainly first to lymph nodes located in level I-III. [A: Adapted from Gibcus 2008 with permission, B: Copyright © Koos Boeve, UMCG, 2019 Groningen].