Radiation therapy and hearing loss

Abstract

A review of literature on the development of sensorineural hearing loss after high-dose radiation therapy for head-and-neck tumors and stereotactic radiosurgery or fractionated stereotactic radiotherapy for the treatment of vestibular schwannoma is presented. Because of the small volume of the cochlea a dose-volume analysis is not feasible. Instead, the current literature on the effect of the mean dose received by the cochlea and other treatment- and patient-related factors on outcome are evaluated. Based on the data, a specific threshold dose to cochlea for sensorineural hearing loss cannot be determined; therefore, dose-prescription limits are suggested. A standard for evaluating radiation therapy-associated ototoxicity as well as a detailed approach for scoring toxicity is presented.

Fig. 1

Mean dose response for sensorineural hearing loss (SNHL) at (a): 4 kHz; (b): 0.5–2 kHz; and (c): all frequencies (0.25–12 kHz). Data from: Figure 3 of Chen et al. (6) (retrospective study; SNHL defined as a ≥20-dB increase in the bone-conduction threshold at ≥1 year; patients received concurrent and adjuvant cisplatin chemotherapy); Figure 1 of Honore et al. (10) (retrospective study; SNHL defined as 20-dB increase in the bone-conduction threshold at ~0.5–6.5 years); Figure 2 of Pan et al. (5) (prospective study; SNHL defined as a 20-dB difference between bone-conduction thresholds for ipsilateral and contralateral ears at 1 year; doses are ipsilateral-ear mean doses minus contralateral-ear mean doses); Table 2 of Oh et al. (8) (prospective study; SNHL defined as a 15-dB increase in the bone-conduction threshold at 1 year; patients received neoadjuvant and concurrent cisplatin chemotherapy); Table 1 and Table 2 of Kwong et al. (7) (prospective study; SNHL defined as a 15-dB increase in the bone-conduction threshold at 1 year; patients received neoadjuvant and concurrent chemotherapy; ears received the full prescription dose; prescriptions were converted to biologically effective dose in 2 Gy fractions using α/β = 3 Gy); Fig 2 of van der Putten et al. (12) (retrospective study; SNHL defined as a 15-dB increase in the average of all pure-tone thresholds at 2–17 years).

Fig. 2

Axial computed tomography image through the skull base. EAC = external acoustic canal; C = cochlea; V = vestibule; IAC = internal auditory canal.