Radiation therapy is the use of ionizing radiation to treat cancer. In external beam radiation therapy, sometimes called EBRT, special equipment is used to aim the radiation directly at cancerous tumors. Radiation therapy can also be delivered internally, called brachytherapy. Radiation therapy is sometimes called radiotherapy, X-ray therapy, XRT, or irradiation.
Cancer cells grow and divide rapidly. Radiation therapy kills fast-growing cells and keeps them from growing and dividing. The amount and intensity of radiation delivered to surrounding normal cells is minimized since treatment is directed to the desired area with much precision. Side effects that occur and their level of severity depend on the area being treated and the intensity (dose) of the radiation treatment.