MRI - Guided Adaptive RadioTHerapy for Reducing XerostomiA in Head and Neck Cancer (MARTHA-trial)

Radiotherapy is the main treatment for locally advanced squamous cell carcinoma of the head and neck (SCCHN). Many advances regarding tumor control and patient survival have been made over the past decades. However, treatment-induced toxicity remains a crucial problem, leading to reduced quality of life and permanent impairment for many survivors. Xerostomia is up to this day the leading cause of late toxicity for these patients. Toxicity has been reduced by implementation of modern image guided radiotherapy (IGRT) and intensity-modulated radiotherapy (IMRT), but the low soft-tissue contrast of routine x-ray image guidance does not allow exact planning adaptation and daily imaging is associated with high radiation exposure. Furthermore, despite the routinely use of IMRT, rates of clinically relevant xerostomia (i.e. grade 2 or worse) are still common and reported in approximately 38%. Recently developed hybrid machines (MRidian®-CE approval since 2016), consisting of a linear accelerator and an integrated low-field MRI, could allow a) better visualization of tumor and organs at risk, such as parotid glands during patient positioning and daily treatment, b) daily imaging without additional radiation exposure, c) narrowest established safety margins for the treatment volumes, and finally d) repetitive adaptation of target volumes according to changes in patient weight and tumor anatomy during the radiotherapy course. These procedures would facilitate a high-precision treatment and help reduce dose exposure of critical structures.