Auditory Outcomes in Patients Who Received Proton Radiotherapy for Craniopharyngioma

Compared to photon-based radiotherapy, protons deliver less radiation to healthy tissue resulting in the potential reduction of late complications such as sensorineural hearing loss (SNHL). We report early auditory outcomes in children treated with proton radiotherapy (PRT) for craniopharyngioma.

Conventional frequency (CF = 0.25-8.0 kHz) audiometry, extended high-frequency (EHF = 9.0-16.0 kHz) audiometry, distortion product otoacoustic emission (DPOAE) testing, and speech-in-noise (SIN) assessments were prospectively and longitudinally conducted on 74 children with a median of 2 post-PRT evaluations (range, 1-5) per patient. The median age at PRT initiation was 10 years, and median follow-up time was 2 years. Ototoxicity was classified using the Chang Ototoxicity Grading Scale (Chang & Chinosornvatana, 2010) and the American Speech-Language-Hearing Association (ASHA) criteria (ASHA, 1994). Comparisons were made between baseline and most recent DPOAE levels, with evidence of ototoxicity based on criterion reductions of ≥ 6 dB. The critical difference values for comparing SIN scores between two conditions (i.e., pre- and post-PRT) were used to determine a significant change between test scores.

At last evaluation, no patients had SNHL in the CF range, and 2 patients had SNHL (Chang Grade 1a) in the EHF range. Based on the ASHA criteria, a decrease in hearing was observed in 0 patients in the CF range alone, in 9 patients in the EHF range alone, and in 15 patients in both the CF and EHF ranges. DPOAE levels decreased at a faster rate at higher versus lower frequencies. For 41 evaluable patients, SIN perception did not decline over time (p = .6463).

At a median follow-up time of 2 years post-PRT, normal hearing was maintained within the CF range. However, subclinical decreases in hearing were observed, particularly in the EHF range and in the DPOAE level; thus, long-term follow-up is recommended to monitor for potential auditory late effects from PRT.