Abstract
This study is to identify significant dosimetric parameters for ear disorders in nasopharyngeal carcinoma (NPC) patients treated with intensity modulated therapy only. Ninety-seven patients with NPC were retrospectively reviewed. Organs at risk (OARs) in the auditory apparatus were contoured. Dose-volume histogram parameters were generated for the Eustachian tube (ET), tympanic cavity (TC), mastoid air cells, vestibular apparatus, cochlea and internal auditory canal (IAC). Ear disorders were rated 0 (none), 1 (mild) or 2 (severe) by a clinician blinded to radiation doses; Grade 2 ear disorders was the study end-point. Multivariate analysis revealed ET.D30 (dose to 30% of ET volume) >52.75 Gy and M.D0.5CC (dose to 0.5 ml of mastoid volume) >41.04 Gy (OR = 3.77, P = 0.012 and OR = 1.27, P = 0.033, respectively) were associated with Grade 2 ear disorders. Our results demonstrated that post-irradiation ear disorders remain a common late toxicity in NPC after IMRT. ET.D30 and M.D0.5CC should be considered during IMRT treatment plan optimization, review and approval.