Is sensorineural hearing loss a possible side effect of nasopharyngeal and parotid irradiation? A systematic review of the literature.

BACKGROUND AND PURPOSE Little has been published about permanent hearing loss due to radiotherapy, thus making it a rather unknown phenomenon. Therefore, we performed a study of the literature over the last 20 years. MATERIALS AND METHODS Sixteen relevant clinical studies were found, reporting mostly on nasopharyngeal or parotid gland treatments. Hearing loss was measured using a pure tone audiogram. Studies were assessed using a simple scoring list. Nine studies were used for further analysis. Data on the pure tone audiogram were pooled. RESULTS Results showed that, especially in the higher frequencies (> or =4 kHz), loss can be measured. When data were pooled, in 42 +/- 3% of the patients a hearing loss was found of 10 dB or more at 4 kHz. Averaged over all measured frequencies the effect is less prominent but still statistically significant (18 +/- 2%). No significant difference between nasopharyngeal and parotid gland treatment was found (P < 0.05). CONCLUSION Only a few studies, mostly concerning small patient numbers, have investigated hearing damage due to radiotherapy. So far there has been no consensus on the subject. However, in this systematic review we found a significant effect. Dose to the inner ear therefore deserves more attention, especially in dose escalation studies and inverse planning.