Dosimetric parameters associated with conductive or sensorineural hearing loss 5 years after intensity-modulated radiation therapy in nasopharyngeal carcinoma

Background: Most previous studies are separate dosimetric analyses of conductive or sensorineural hearing loss, and they are not conducive to a comprehensive assessment of auditory radiation damage.

Aims/objectives: Our study aimed to evaluate the long-term incidence of sensorineural hearing loss (SNHL) or conductive hearing loss (CHL) in patients with nasopharyngeal carcinoma (NPC) after intensity-modulated radiation therapy (IMRT), and to investigate the relationship between SNHL or CHL and patient factors, treatment-related factors, and radiation dose parameters.

Material and methods: Seventy patients (117 ears) with NPC, who were also treated with IMRT in our hospital from 2006 to 2014, were retrospectively analyzed. Radiation doses to the Eustachian tube (ET), middle ear (ME), cochlear (Co), and internal auditory canal (IAC) were assessed. Pure tone audiometry and impedance audiometry were performed before and during the follow-up period. The relationships between low-frequencies (0.5–2?kHz) or high-frequency (4?kHz) SNHL/CHL and radiotherapy dose parameters were analyzed.

Results: Of the 117 ears studied, 7.69% had low-frequency SNHL, 35.9% had high-frequency SNHL, 23.93% had low-frequency CHL, and 18.80% had high-frequency CHL. The incidence of high-frequency CHL was higher in the T4 group than in the T (1–3) group (p?D_max?>?42.13?Gy or IAC D_mean?>?32.71?Gy, the risk of high-frequency SNHL increased in NPC patients. When ME D_max?>?44.27?Gy, ME D_mean?>?29.28?Gy, or ET D_max?>?57.23?Gy, the risk of high-frequency CHL in NPC patients increased.

Conclusions and significance: SNHL and CHL remain common ear complications after IMRT for NPC. IAC D_max, IAC D_mean, ME D_max, ME D_mean, and ET D_max all need to be carefully considered during the IMRT treatment protocol.