141 8 Introduction Head and neck cancer (HNC) is the seventh most common cancer worldwide, accounting for an estimated 650,000 new cases and 350,000 deaths every year.1 HNC is most often caused by alcohol and/or tobacco use, or the human papilloma virus (HPV).2 Curative treatment options for HNC include surgery, radiotherapy (RT) and chemo radiation (CRT). Treatment extent and intensity vary, and the choice of treatment modality depends on tumor site, tumor stage, comorbidities, and wishes and expectations of patients.3,4 Surgery may compromise lingual mobility, strength, and muscle coordination in the head and neck region.4-6 High-intensity radiation treatment regimens have resulted in improved survival and tumor control, but may also lead to acute effects such as pain, mucositis, and decrease in saliva production, and late effects such as trismus, masticatory deficits, dysphagia (swallowing dysfunction), and xerostomia.4,7,8 Chemotherapy can add to these effects by increasing oral mucositis, nausea, vomiting, loss of appetite, and xerostomia.9 These side effects occur in a considerable proportion of patients after HNC treatment despite efforts to spare structures related to oral food processing, salivary function, and swallowing.7,10 During the food process, several muscles, nerves and connective tissue structures need to work together to break down food into smaller particles which bind to each other through saliva, and form a food bolus ready for swallowing and digestion.11,12 The number of teeth and occlusal units are of great importance to grind and break down food. Tooth loss, the presence of cavities, inadequate restorations, malocclusion or periodontal disease can adversely affect chewing function and thereby also swallowing.13,14 Side effects of treatment may have a negative influence on swallowing function and thereby on the ability to eat and drink, which in turn impact health related quality of life (QoL) of patients.1,15,16 To evaluate patient reported outcomes (PROs) regarding dysphagia, several tools are available such as the swallowing subscale of the European organization for research and treatment of cancer quality of life questionnaire (EORTC QLQ-H&N35), the M.D. Anderson Dysphagia Inventory (MDADI),17,18 and the Swallowing quality of life questionnaire (SWALQOL).16 An important study using the EORTC QLQ-H&N35 to assess swallowing (n=2458) provided a survey at baseline, and 4 and 12 months post-baseline.19 This study included all possible patients with HNC (all curative treatment options and tumor sites). Swallowing was diminished especially 4 months after treatment. Factors associated with swallowing and social eating were: tumor site, age, treatment, smoking, socio-economic status, and sex.19 Unlike the EORTC QLQ-H&N35 questionnaire (which only has a swallowing and social eating subscale), the SWAL-QOL questionnaire includes multiple subscales to assess swallowing related quality of life. Multiple studies assessed swallowing as measured with the SWALQOL, either as prospective cohort study to investigate swallowing differences over time,7,20-