Differences In Parotid Dosimetry in Whole Brain Irradiation Plans Covering Cervical Vertebrae One Versus Two

Background: Whole-brain radiation therapy (WBRT) is one of the most frequently employed therapies in radiation oncology. It is commonly used in palliative care to manage cases with several brain metastases. WBRT is often provided utilizing opposing lateral fields with 6 MV photons and gantry-rotation or multi-leaf collimators (MLCs) designed to spare the lenses bilaterally.Objectives: The present work aims to evaluate the dose received by parotid glands (PG) in WBRT in plans covering cervical vertebrae one versus two.Patients and methods: This clinical trial was conducted on 18 patients who received WBRT in the Clinical Oncology and Nuclear Medicine Department (Linac unit) at Zagazig University Hospitals.Results: There was a significant correlation between the C1 plan and the C2 plan concerning PTV mean dose, but there was a non-significant correlation regarding PTV V95, V90, and V105. Statistical analysis of results showed a significant correlation between plan C1 and plan C2 regarding total PG that received more than 25 Gy and one of the glands that received more than 20 Gy. There was a non-significant correlation between plan C1 and plan C2 regarding the PG volume, but there was a highly significant correlation regarding the PG mean dose, V20, and V25.Conclusion: The dose given to the PGs increases when the inferior border of a typical whole-brain field is extended to include the C2 vertebral body. This is expected to lead to a higher incidence of xerostomia.