Comparison of Dosimetry of Organs at Risk for the Treatment of Nasopharyngeal Cancer Using Two Methods of Helical Tomotherapy and Three Dimensional Conformal Radiation Therapy

Nasopharyngeal cancer is one of the common head and neck cancers and the main treatment for this type of cancer is radiotherapy. The purpose of this study is to investigate and compare the dose of organs at risk in two adaptive three-dimensional methods (3D-CRT) and helical tomotherapy (HT) in patients with head and neck cancers.

This study is a cross-sectional experimental retrospective study and to conduct this study, CT scan images (Computed Tomography) of 16 patients with early stages of NPC with an average age range of 16-81 years (42.7 ± 16.3) those were randomly selected. The organs at risk and their target volume were contoured and the treatment plan of the patients was done for both HT and 3D-CRT methods. In the end, using a Volume-Dose histogram (DVH), the dosimetry variables of organs at risk and target volume were extracted and compared with each other.

Compared to 3D-CRT, the HT method improved the homogeneity index and concordance index. It also significantly reduced the dose of the studied OARs compared to 3D-CRT, although the dose of some of these organs exceeded the prescribed dose limit.

HT method is a better technique for treating nasopharyngeal cancer patients who are candidates for radiotherapy due to better coverage of the target volume and also, better performance in preserving OARs compared to the 3D-CRT method.