Radiothérapie conformationnelle avec modulation d’intensité des cancers des voies aérodigestives supérieures, dose de tolérance des tissus sains : appareil cochléovestibulaire et tronc cérébral

Abstract

Modern techniques such as intensity modulated radiation therapy (IMRT) have been proven to significantly decrease the dose delivered to the cochleovestibular apparatus, limiting consecutive toxicity especially for sensorineural hearing loss. However, recent data still report a 42% rate of radio-induced hypoacusia underscoring the need to protect the cochleovestibular apparatus. Due to the small size of the cochlea, a precise dose–volume analysis could not be performed, and recommendations only refer to the mean dose. Confusing factors such as age, concomitant chemotherapy, primary site and tumor stage should be taken into account at the time of treatment planning. (Non-coplanar) VMAT and tomotherapy have been proven better at sparing the cochlea in comparison with 3D CRT. Brainstem radio-induced injuries were poorly studied because of their infrequency and the difficulty of distinguishing between necrosis and tumor progression in the case of a primary tumor located at the base of skull. The following toxicities have been described: brainstem focal radionecrosis, cognitive disorders without dementia, cranial nerve injuries and sensori motor disability. Maximal dose to the brainstem should be kept to < 54Gy for conventional fractionation. This dose could be exceeded (no more than 10mL should receive more than 59Gy), provided this hot spot is located in the peripheral area of the organ.