Introduction: The purpose of this study was to develop a statistical model for prediction of radiation induced sensorineural hearing loss (SNHL) induced by radiotherapy in patients with brain tumors.
 
Materials and Methods: CT scan of 18 patients (10 males and 8 females) with brain tumor who were referred to Radiation Center of Milad Hospital in Isfahan in 2017 was used. For each patient, audiometric evaluation was performed before and 12 months after treatment at frequencies of 500-8000 Hz. The cochlea contouring on the patient's CT scan was performed by an oncologist using TiGRT therapy treatment planning system. Dose-volume histograms (DVH) for 2D and 3D treatment plans were calculated and compared. In order to predict SNHL after radiotherapy, a model was developed using patient’s data and regression statistical method based on a logarithmic function. Significance of factors influencing SNHL was also investigated.
Results:
The dose delivered to cochlea was similar in 2D and 3D treatment plans (P values = 0.256). During the 12 months after treatment, relationship between SNHL and cochlea dose, age, hearing threshold before treatment, and sound frequency were evaluated. The developed regression model showed the significance of sound frequency on the relationship between age and dose delivered to cochlea on auditory level of the patients after treatment.
Conclusion:
Effect of dose delivered to auditory system depends on patient’s age and hearing threshold before treatment, as well as sound frequency. The degree of hearing loss in patients was higher at higher frequencies