Early Response Evaluation of Proton Therapy by PET-imaging in Squamous Cell Carcinoma Located in the Head and Neck

The goal of this project is to develop and characterise an imaging strategy for biology-guided individualisation of the proton therapy plan to improve patient outcome and quality-of-life. Positron-emission tomography (PET) studies reflecting glucose metabolism, hypoxia and physical changes of proton-irradiated tumour tissues will be performed. Patients with head and neck cancer will be studied, as these individuals frequently experience recurrences within the radiation field, often with limited therapeutic options. Severe side-effects and functional impairment, deteriorating patients' quality-of-life, limited the use of dose-escalation in recent feasibility studies of photon therapy guided by individual PET-response. However, proton therapy, currently being introduced in the Netherlands, improves the precision of radiotherapy and thereby limits the side-effects caused by irradiation of neighbouring healthy tissues. Therefore, in proton therapy dose-escalation to improve patient outcome is less restricted by toxicity. Using PET-studies of two hallmarks of radioresistance, glucose metabolism and hypoxia, side-by-side, before and early in-treatment, the predictive ability of both PET-techniques for local recurrence-free survival will be compared. A treatment plan adapted to the individual response measured by both procedures and compute tumour-dose and toxicity, will be simulated, thereby substantiating feasibility of image-guided adaptive replanning. Simultaneously to biological responses, proton therapy-induced physical changes will be studied. These atomic changes, dependent on tissue-composition and dose-deposition, are measurable by PET. It is expected that activation-PET to measure tissue-changes during therapy, a potential new biomarker of treatment efficacy, toxicity but also accuracy of treatment plan execution. Activation-PET will be related to earlier-mentioned PET-imaging of metabolism. This clinical-technological project paves the way for an interventio