J Cancer 2016; 7(3):276-282. doi:10.7150/jca.13183 This issue
1. Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, Guangdong Province, People's Republic of China
2. Department of Medical Statistics and Epidemiology & Health Information Research Center & Guangdong Key Laboratory of Medicine, School of Public Health, Sun Yat-sen University, Guangzhou 510080, Guangdong Province, China
3. Department of Radiation Oncology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510120, Guangdong Province, China
4. Department of Pathology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, Guangdong Province, People's Republic of China
† These authors contributed equally to this manuscript.
Background: To identify predictors for development of mastoiditis after intensity-modulated radiation therapy (IMRT) in nasopharyngeal carcinoma (NPC).
Methods: Data for 146 NPC patients treated with IMRT was retrospectively reviewed under institutional ethics committee approval. Clinical factors associated with mastoiditis were analyzed. Dose-volume histogram analysis was performed for the Eustachian tube, tympanic cavity, mastoid air cells, cochlea, internal auditory canal and vestibular apparatus to relate doses to radiographic changes in the mastoid. Mastoiditis was assessed using magnetic resonance imaging and was classified as Grade 0 (none), 1 (mild), 2 (moderate) or 3 (severe); Grade 3 mastoiditis was the study end-point.
Results: Eighty-eight ears (36%) had radiation-induced mastoiditis: 38/244 (15.6%) mastoid complexes had Grade 1-2 mastoiditis and 50/244 (20.5%) mastoid complexes had Grade 3 mastoiditis. Multivariate analysis revealed a mastoid mean dose > 35.93 Gy (odds ratio [OR]=4.22, P=.003), Eustachian tube mean dose > 53.43 Gy (OR=2.16, P=.034) and advanced T category (T3 and T4; OR=10.33, P=.032) were negative prognostic factors for Grade 3 mastoiditis.
Conclusions: Radiation-induced mastoiditis remains a common late toxicity in NPC after radiotherapy. The mean dose to the mastoid air cells and Eustachian tube should be limited to reduce the risk of radiation-induced mastoiditis.
Keywords: dose-volume histogram, intensity-modulated radiotherapy, mastoiditis, nasopharyngeal carcinoma, organs at risk.