**1.2 Head and neck cancer treatment**

Patients with HNC can be treated with (a combination of) surgery, radiotherapy, chemotherapy, proton therapy, immunotherapy, or photodynamic therapy (PDT). The choice of treatment depends on the location and the size of the tumor (TNM classification). Despite improved radiotherapy techniques, the anatomical structures, including muscles and tissue around the primary tumor, can still be damaged by the tumor itself or the treatment [6–8]. Well-known (negative) side effects of the HNC treatment are xerostomia, sticky saliva, mucositis, altered taste, weight loss, pain, trismus and tissue loss due to fibrosis. Long-term functional problems such as swallowing problems (dysphagia), voice or speech problems, and trismus can harm patients' quality of life [9].
