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

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. The authors generated VMAT plans for 14 post operated oral cancer patients, where primary disease crossed midline or nodal stage ≥ 2. The doses to the moderate high-risk volume of the clinical target volume (CTV) and planning target volume (PTV) were 60Gy in 30 fractions. The low-risk volume received a dose to the CTV and PTV of 54Gy in 30 fractions. Plans were made for each patient, and the dose to D95 and D98 of target volumes was analyzed. The mean dose of the parotid and parotid minus PTV volumes were analyzed and compared with target doses (D98 & D95).  Median dose to the ipsilateral parotid gland was 54.45Gy and to the ipsilateral parotid gland minus PTV was 45.60Gy while to the contralateral parotid gland median dose was 16.31Gy, (mean is ranging from 14.01 to 17.06Gy) and to the contralateral parotid gland minus PTV was 14.92 (mean is ranging from 12.42 to 15.18Gy) after achieving the 95% coverage of PTV. 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.