Dosimetric evaluation of cochlea dosage in viiatientsviiapy of viiatients with nasopharyngeal cancer

Background and Aim: The standard treatment method for nasopharyngeal cancer is radiotherapy, and one of the side effects of radiotherapy irradiation is the factor of hearing impairment resulting from high doses given to the cochlea. The aim of this study is to provide a potential hearing in nasopharyngeal cancer patients by providing the maximum possible cochlea protection without compromising the dose coverage in the planned treatment volume. Material and Methods: In our study, while the same treatment dose was applied at the target volume (PTV) with different radiotherapy techniques, the doses formed in the cochlea and other organs at risk (RAO) were compared. For this purpose. Treatment plans were created using 3 different techniques (3BKRT, IMRT, VMAT). All schemes were optimized for RAO's (left-right cochlea, Brainstem, medulla spinalis, left-right lenses) to receive a minimum dose. Cochlea doses for PTV's were compared using the dose-volume histogram (DVH) for each plan. Results: The VMAT technique was found to be significantly superior to 3BKRT and IMRT. VMAT significantly reduced the dose of cochlea compared to 3BKRT and IMRT. When we examine the lowest doses for other RAO's; VMAT for brainstem, VMAT for medulla spinalis, VMAT for left-right parotid and VMAT for left-right were found to provide better dose protection. Conclusion: In patients with nasopharyngeal cancer, the VMAT technique provides better protection in target volume irradiation compared to IMRT and 3BKRT, and seems to be more advantageous in terms of cochlea protection. Keywords: 3DCRT, IMRT, VMAT nasopharyngeal cancer, cochlea