Despite uniform histopathological definition the response of locally advanced squamous cell carcinomas of the head and neck (HNSCC) to ionizing radiation differs greatly with locoregional recurrences burdening this patient population. The addition of concurrent chemotherapy and the use of altered fractionation schedules has significantly increased locoregional control and overall survival over the last decade however, this has come at the cost of increased acute and late toxicity, preventing further treatment intensification in all patients. If the investigators want to increase the therapeutic index of HNSCC, we need to be able to tailor the treatment more individually to each patient. The project aims at developing a prognostic model for head and neck cancer patients based on the combination of known clinical parameters with 1) genetic characteristics of the tumor and 2) parameters derived from diffusion weighted and dynamic contrast enhanced magnetic resonance imaging (MRI) obtained before and during treatment. The investigators plan a prospective trial where 120 patients with locally advanced head and neck cancer treated with chemoradiotherapy will be included. Prior to treatment biopsy material will be collected for genetic analysis and before and during treatment functional MRI with diffusion weighted and dynamic contrast enhanced imaging will be performed. All patients will be followed up multidisciplinary afterwards with follow-up of tumor status and toxicity.