Radiation uses special equipment to deliver high-energy particles, such as x-rays, gamma rays, electron beams or protons, to kill or damage cancer cells. Radiation (also called radiotherapy, irradiation, or x-ray therapy) can be delivered internally through seed implantation or externally using linear accelerators (called external beam radiotherapy, or EBRT). Radiation may be used as a solitary treatment or with surgery and/or chemotherapy. The equipment used to deliver the radiation therapy is called a linear accelerator. The linear accelerator has a moveable arm, which enables the radiation to be focused on the part of your body where the cancer is located. Developments in EBRT equipment have enabled physicians to offer conformal radiation. With conformal radiation, computer software uses imaging scans to map the cancer three-dimensionally. The radiation beams are then shaped to conform, or match, the shape of the tumor.

Radiation works by breaking a portion of the DNA of a cancer cell, which prevents it from dividing and growing. Radiation therapy can be systemic, meaning it moves throughout your bloodstream. Systemic therapies are usually given as an injection into a blood vessel or are taken as a pill. Systemic treatments expose your entire body to cancer-fighting medication. Radiation therapy is typically given as a "local" treatment however, meaning it affects only the part of the body that needs therapy.