There are only a few works in the literature that correlate the circulating levels of vitamin D with the prognosis or development of toxicity in treated HNSCC patients with radical intent radiation therapy. These small studies have highlighted a worse outcome and greater toxicity in patients with low vitamin D levels. The study aims to study the variations in circulating levels of vitamin D in a multicenter cohort of patients with HSNCC prospectively collected and to evaluate the impact of vitamin D levels at diagnosis on the development of toxicity and on disease outcome
The goal of this observational study is to learn about relation between vitamin D levels in subjects with head and neck cancer. The main question it aims to answer are:~variation of vitamin D levels in the study population at different time points~relation between therapy side effects and vitamin D level~relation between disease outcome and vitamin D level Participants will be followed as per clinical practice