Radiation therapy is the use of high-energy radiation, such as X-rays, to destroy cancer cells and shrink tumors. Radiation may come from a machine outside the body (external radiation therapy). Radiation can also be given from inside your body (internal radiation therapy). For example, brachytherapy uses radiation implants that are placed in or near the cancer. Systemic radiation therapy is given by a pill or injection. And intraoperative radiation therapy is given inside the body during an operation.

Radiation therapy is standard treatment for many types of cancer. It may be used in combination with other treatments, such as surgery, chemotherapy, or immunotherapy.