Analysis of anatomical factors controlling the morbidity of radiation-induced otitis media with effusion.

Abstract

To analyze the anatomical factors controlling the morbidity of radiation-induced otitis media with effusion (OME) and determine how to best preserve middle ear function when treating nasopharyngeal carcinoma (NPC). Forty patients with nasopharyngeal carcinoma undergoing 3-D radiotherapy (RT) planning and curative RT were analyzed retrospectively. The difference in dosage over the middle ear cavity and the isthmus of the Eustachian tube (ET) was evaluated. Pure tone audiometry and impedance audiometry tests were performed before and after RT. Mean dosages over the isthmus of the ET for acoustic impedance and pure tone audiometry were recorded. Differences in dosage among the three classifications of unchanged, improved, and worsened ears were statistically significant. There was a correlation between the morbidity of radiation-induced OME and the radiation dosage over the middle ear cavities. Decreased OME morbidity was observed when the dosage over the isthmus of the ET was below 52 Gy and the dosage over middle ear cavity was below 46 Gy.