Immunological Function After Radiation With Either Proton or Photon Therapy

This is a pilot prospective observational cohort study, comprising patients with head and neck cancer (HNSCC) treated with standard of care definitive (chemo)radiation either with photons or protons. Patients will be assigned for protons or photons based on the guidelines of the National Indication Protocol for Proton therapy of the Netherlands. Immunological function will be evaluated by the collection of peripheral blood mononuclear cells (PBMCs). Blood samples will be collected at baseline, during (chemo)radiation (end of week 3 and/or before week 4 of treatment) and after completion of (chemo)radiation (week 9, week 12, week 20, week 34 and week 60, respectively 1 week, 5 weeks, 3 months, 6 months and 12 months after completion of (chemo)radiation). To quantify immunological function, PBMCs collected during (chemo)radiation and after (chemo)radiation will be compared with that before (chemo)radiation (week 0), using IFN-γ-ELISPOT to screen for the presence of antigen-specific T-cell responses. Furthermore, flow cytometry panels will be used to determine global changes in immune cell proficiency. Histological evaluation will take place at baseline and week 3 to examine changes in immune infiltration within tumour tissue during proton versus photon (chemo)radiation. This biopsy part of the study is optional for the patient. Archival tissue from the biopsy that was taken at diagnosis will be used for the baseline assessments. Biopsy at week 3 week will be taken for all patients who agree to participate in this optional part of the study.