Rthp-15. incidence of mastoid effusion in patients receiving photon radiation therapy for glioblastoma

Radiation therapy (RT) induced mastoid effusion has been documented after-RT to the cranium, or head and neck. Grade 2/3 mastoid effusions (G2/3M) have been documented in nasopharyngeal cancers at rates of 20 – 30% and are correlated with the mean dose and volume of mastoid irradiated. However, mastoid effusions in patients with gliomas have not been well characterized. We hypothesized that different radiation volumes, tumor location, and the addition of radiosensitizing chemotherapy may impact the incidence and severity of mastoid effusions in patients irradiated for glioblastoma. A retrospective analysis of patients treated for glioblastoma from 2010 to 2015 was conducted. Patients received a median dose of 60Gy to the primary lesion with concurrent temozolomide. Mastoid opacification on T2-weighted MR images was a surrogate for effusion and scored as Grade 0 (not seen), Grade 1 (mild), Grade 2 (moderate), or Grade 3 (severe). Charts were reviewed for clinical signs or symptoms of ear disorders. Unpaired t-test was used to compare groups. A total of 51 patients were included. Prior to RT, 19.6% (10/51) had baseline mastoid effusions. An additional 9.8% (4/41) developed G2/3M, with an average time to onset of 1mo (range 0.5 – 3mo) and resolution at 3.7mo (range 3 – 7mo) after completion of RT. Mastoid D50 (dose to 50%) was 12.8Gy vs. 30.5Gy(p=0.027), with a mean mastoid dose of 16.9Gy vs. 30.5Gy(p=0.454) for Grade 0/1 vs. G2/3M, respectively. Three patients with G2/3M experienced clinical sequela, including otalgia, sensation of fullness, serous otitis media, and mastoid tenderness. The incidence of mastoid effusion in patients with glioblastoma was lower than in patients treated for head and neck cancers. Though less common in gliomas, radiation induced mastoid effusion is an important consideration in patients who present with middle ear signs and symptoms after RT.