Radiation dose to otologic structures during head and neck cancer radiation therapy

Background Otologic structures are often contained within head and neck can cer radiation treatment ports. The dosimetry to otologic structures has not been routinely analyzed and radiation treatment planning does not currentl y attempt to specifically avoid the inner ear structures when dosimetry is calculated. Recent studies demonstrate that up to 30% of patients experienc e sensorineural hearing loss on multimodality therapy with cisplatin and ra diation. Methods: In the current case series, radiation dosimetry to otologic struct ures was calculated from computed tomogram treatment plans on patients. Fif teen nasopharyngeal, oral cavity, oropharyngeal, and hypopharyngeal cancer patients were analyzed. Results: Between 8% and 102% of the total dose is delivered to the petrous bone/cochlea, with 4 of 15 patients getting more than 50% of the dose to at least one cochlea, The mastoid air cells received between 3% and 75% of th e total dose, with higher doses being delivered to patients with bulky high neck metastases or nasopharyngeal tumors, The eustachian tubes received be tween 2% and 102% of the total dose, with 10 of 15 patients receiving more than 50% of the dose to this anatomic site, Conclusion: We conclude that the cochlea and eustachian tubes receive signi ficant radiation during treatment, particularly in nasopharyngeal cancer pa tients. Careful design of radiation treatment ports may allow for the reduc tion of radiation to hearing structures.