Prediction and prevention of radiation-induced swallowing dysfunction

Radiotherapy of head and neck cancer may lead to multiple side effects with major impact on quality of life. The most important side effects are dry mouth and swallowing problems. With new radiotherapy techniques it is possible to spare the salivary glands to prevent a dry mouth. At the beginning of this research little was known about which structures (organs at risk) cause swallowing problems and should therefore be spared during radiotherapy.The purpose of this thesis was to optimize the radiotherapy technique to decrease and prevent swallowing problems.We started to determine which radiation dose factors in which anatomical structures explained swallowing problems six months after finishing radiotherapy treatment. Two structures were identified: the superior swallowing muscle (pharyngeal constrictor muscle superior) and the upper part of the larynx (supraglottic larynx). Next we improved the radiotherapy technique by sparing these two structures as much as possible (swallowing sparing radiotherapy) and by doing so we showed that sparing these structures resulted in less swallowing problems six months after radiotherapy. However, in only 50% of the patients it is possible to spare the dose in these structures without decreasing the dose to the tumour or increasing the dose to the other organs at risk. Therefore there is still room for improvement. In this regard, the most promising technique is proton therapy. The results of this thesis can also be used to select patients who will benefit most from the swallowing sparing radiotherapy and other newly developed techniques, like proton therapy