A prospective longitudinal study on radiation-induced hearing loss.

Recent clinical reports indicate that patients receiving radiotherapy that includes the auditory system in the treatment volume are likely to develop an irradiation-induced hearing loss. Although the early, presumed reversible, conductive hearing impairment due to secretory otitis media following radiotherapy is a sequela well known by radiation oncologists, permanent hearing loss, both conductive and sensorineural, is believed to be rare. A prospective study was performed enrolling patients receiving postoperative radiotherapy for unilateral parotid tumors. Audiometric results prior to irradiation were compared with those obtained 2 years later. Up to 50% of the patients (9 of 18) developed a clinically relevant hearing loss in the irradiated ear, both conductive and/or sensorineural. The contralateral ear remained unaltered. The hearing loss was permanent in 6 patients (33%) and affected their quality of life. The data suggest that changes occur in the inner ear as well as in the auditory nerve and auditory brain stem with conventional irradiation schemes with daily fractions of 2 to 2.5 Gy with a total dose of 50 Gy.