Objective and subjective evaluation of effectiveness of Cochlear sparing in Highly conformal head and neck radiotherapy

Background: Radiotherapy for head and neck cancers often results in radiation to the cochlea increasing the risk of sensorineural hearing loss (SNHL), which can significantly impair quality of life. This study aimed to evaluate the effectiveness of cochlear-sparing volumetric-modulated arc therapy (CS-VMAT) in reducing radiation-induced ototoxicity and if we need to reassess the conventional cochlear dose constraint of <45 Gy. Methods: In this prospective observational study, 29 patients receiving CS-VMAT for head and neck malignancies were assessed. Bilateral cochlear doses were analyzed for 58 ears. Objective auditory evaluations (pure tone audiometry [PTA], distortion product otoacoustic emissions [DPOAE], tympanometry) and subjective assessment (Hearing Handicap Inventory for Adults [HHIA]) were conducted at baseline and 3 months post-treatment. Dosimetric comparisons were made between dose groups (<25 Gy vs. ≥25 Gy). Results: CS-VMAT achieved mean cochlear doses <25 Gy in 51.7% of cases without compromising target volume coverage. At 3 months post-treatment, PTA revealed hearing deterioration in 18 ears (31%), with statistically significant worsening in those receiving >25 Gy mean cochlear dose (p<0.01). DPOAE and tympanometry showed trends toward cochlear dysfunction and middle ear changes but were not statistically significant. HHIA scores indicated a decline in hearing-related quality of life in 31% of patients (p<0.01), all reported fromthose who received > 25 Gy. Conclusion: This study demonstrates that cochlear doses >25 Gy are associated with early hearing loss with reduced quality of life. While CS-VMAT effectively reduces cochlear exposure, the current 45 Gy threshold may not adequately prevent hearing impairment. A revised dose constraint closer to 25 Gy may be more clinically relevant, warranting further investigation in larger and longer-term studies.