Potential benefits of intensity-modulated proton therapy in head and neck cancer

Head and neck cancer target volumes are often complex shaped, large and surrounded by many critical and vital structures. Hence, radiotherapy of the head and neck region is frequently associated with a variety of radiation-induced acute and late side effects that adversely affect quality of life. The two most important radiation-induced late side effects significantly affecting patients’ quality of life are xerostomia (the sense of a dry mouth) and swallowing dysfunction.
Introduction of advanced photon-based radiotherapy techniques have enabled better dose conformation to the target volume while reducing the normal tissue dose. Multiple studies have shown that compared with conventional radiotherapy, photon-based intensity-modulated radiotherapy (IMRT) can improve avoidance of the organs at risk (OARs) relevant for xerostomia and swallowing dysfunction. IMRT, however, does not always result in substantial improvements regarding sparing of those OARs. Hence, further dose reductions in all relevant OARs by using more advanced radiotherapy techniques, like proton therapy (protons have superior beam properties over photons), can help to reduce the probability of xerostomia and swallowing dysfunction.

With the individual in silico planning comparison studies described in this thesis the potential benefits of different intensity-modulated proton therapy (IMPT) techniques in head and neck cancer have been explored, in relation to the current standard (IMRT), regarding reduction of xerostomia and swallowing dysfunction. The presented results indicate that IMPT may substantially improve sparing of the relevant OARs and hence may contribute to an improved quality of life during and after curatively intended radiotherapy.