National Cancer Institute

external beam radiation therapy

(... RAY-dee-AY-shun THAYR-uh-pee)
A type of radiation therapy that uses a machine outside the body to send high-energy radiation beams toward the area of the body with cancer. It is used to treat many types of cancer. It may also be used to shrink tumors to treat pain and other problems caused by the tumor, such as trouble breathing or loss of bowel and bladder control. Also called external radiation therapy.