Late visual and auditory toxicity of radiotherapy for nasopharyngeal carcinoma

Classical irradiation of carcinoma of the nasopharynx involves large fields and high doses; therefore, significant late toxicity and late side effects are to be expected. Given the fact that nasopharyngeal carcinoma (NPC) is a relatively radiosensitive disease and a significant proportion of patients are long-term survivors, late visual and auditory complications of treatment are of utmost concern for patients and radiation oncologists. The aim of this study was to evaluate the long-term visual and auditory toxicity in patients treated with radiotherapy for NPC.

Forty-three long-term survivors (including 11 children), following definitive radiotherapy for NPC, underwent a thorough visual and auditory evaluation 2-22 years after their treatment. Ophthalmological examination consisted of anamnesis of dry eye syndrome and visual acuity, visual acuity testing, slit-lamp examination, Schirmer test, fundus examination, and intraocular pressure measurement, as well as fluorescein angiography in patients with pathological vascular findings in the fundus examination. Audiological evaluation included anamnesis of hearing loss, tinnitus or vertigo, examination of the ears and nasopharynx, audiogram, and tympanogram.

Radiation retinopathy was found in 16% of patients by fundus examination, with one patient (2.3%) developing blindness. Severe dry eye syndrome was present in 26%. Fifty-six percent had some degree of hearing impairment, with 74% showing severe sensorineural hearing loss. Fifty-eight percent of patients reported tinnitus and 26% reported suffering from dizziness. Radiation retinopathy as well as all manifestations of auditory toxicity were found to bear a direct correlation with dose per fraction.

Unless there is tumor involvement, the orbital contents should be completely excluded from the target volume. Auditory toxicity is significant when treating NPC with two-dimensional techniques.