Radiation therapy uses ionizing radiation to control malignant cells. It works through direct and indirect effects on cells, causing damage to DNA. A radiation treatment plan considers the tumor location and size, areas to treat, number of fractions, total days, and patient tolerance. Fractionation gives normal cells time to recover while further damaging tumor cells. External beam radiation delivers high-energy beams while brachytherapy places radioactive sources inside the body. Side effects include mucositis, loss of taste, xerostomia, radiation caries, and osteoradionecrosis.