Quantitative Analysis of Parotid Sparing and Reducing Xerostomia Using Volumetric Modulated Arc Therapy in Oral Cancer Patients

Introduction: In head and neck cancer (HNC) radiotherapy, parotid, submandibular, and minor salivary glands are often incidentally irradiated. Hence, Xerostomia is the most significant disabling side-effect, to improve the quality of life, it should be reduced. The study was to evaluate the parotid dose and PTV coverage in post operated Oral cancer patients using Volumetric Modulated Arc Therapy (VMAT) technique.Material and Methods: The authors generated VMAT plans for ۱۴ post operated oral cancer patients, where primary disease crossed midline or nodal stage ≥ ۲. The doses to the moderate high-risk volume of the clinical target volume (CTV) and planning target volume (PTV) were ۶۰Gy in ۳۰ fractions. The low-risk volume received a dose to the CTV and PTV of ۵۴Gy in ۳۰ fractions. Plans were made for each patient, and the dose to D۹۵ and D۹۸ of target volumes was analyzed. The mean dose of the parotid and parotid minus PTV volumes were analyzed and compared with target doses (D۹۸ & D۹۵). Results: Median dose to the ipsilateral parotid gland was ۵۴.۴۵Gy and to the ipsilateral parotid gland minus PTV was ۴۵.۶۰Gy while to the contralateral parotid gland median dose was ۱۶.۳۱Gy, (mean is ranging from ۱۴.۰۱ to ۱۷.۰۶Gy) and to the contralateral parotid gland minus PTV was ۱۴.۹۲ (mean is ranging from ۱۲.۴۲ to ۱۵.۱۸Gy) after achieving the ۹۵% coverage of PTV.Conclusion: Better sparing of contralateral parotid glands with the help of VMAT technique in post-operative HNC patients is possible, which can prevent xerostomia in most patients.

Keywords:

Parotid , Xerostomia , oral cancer