Permanent unilateral hearing loss after radiotherapy for parotid gland tumors.

BACKGROUND The purpose of this retrospective study was to determine the long-term effects of radiotherapy on hearing function in patients who underwent parotidectomy and postoperative radiotherapy for unilateral tumors of the parotid gland. METHODS An extensive set of tests was used to measure hearing loss. The mean dose on middle ear, cochlea, and Eustachian tube was estimated with a CT-planning system. RESULTS A hearing loss of > or = 15 dB in 3 frequencies was found in 32% of the 52 patients included in the study. Patients with an asymmetrical hearing loss received a higher mean dose on the hearing structures (p < .002). The threshold dose for clinically relevant hearing loss was found at 50 Gy on the cochlea and Eustachian tube. CONCLUSIONS Radiation-induced hearing loss is a common complication. A mean dose of > 50 Gy on the cochlea should be avoided.