Positional changes in parotid glands during head and neck radiation therapy

Introduction: Xerostomia is the most common complication due to radiation–induced damage to salivary glands in head and neck cancer radiotherapy and it reduces quality of life. Parotid glands are main glands which they are account for secretion of stimulated saliva. Studies have demonstrated that mean tolerance parotid’s radiation dose under 26-30 Gy result in an increase in the number of patients who keep more than 25% of their initial stimulated saliva flow. But some studies have indicated that radiation in head and neck region causes positional changes in parotid glands. It may increase the parotid gland’s portion of radiation dose and consequently increases xerostomia complication. In this study radiation-induced positional changes in parotid glands are evaluated. Materials and Methods: In this study 10 head and neck cancer patients were studied. CT scan images obtained from them before and also after radiotherapy. Then position of parotid glands was evaluated by treatment planning software. In this purpose distance of parotid’s center of mass to radiopaque marker, located on patient’s mask, was measured. Then its radiation– induced positional changes were calculated. Results: In this study parotid mean dose was 4252±853 cGy. At this analyze at the end of radiotherapy, positional changes of parotid glands were observed. Conclusion: It seems that radiotherapy at head and neck regions may result in positional changes for parotid glands. Then there is probable that more portions of parotid glands involve in radiation fields and increase the damage to them. Therefore more attention to parotid glands, as an organ at risk, is necessary at planning treatment of head and neck cancers.