Definitions for "External beam radiation therapy"
Radiation therapy administered from an energy source outside the body and directed to a target inside the body
Radiation treatment for prostate cancer, where a high dose of radiation is delivered from an outside source into the prostate to kill the cancer. The radiation must transverse through healthy tissue to reach the cancerous area. Treatments are generally 5 days a week for 7-8 weeks. Each treatment last only a few minutes. Newer forms of external beam radiation, called three-dimensional conformal radiation (3D-CRT) and intensity modulated radiotherapy (IMRT) more accurately target the prostate and are considered the preferred method when using external beam radiation for the initial treatment of prostate cancer. With these newer therapies the patient is immobilized and subjected to radiation beams aimed from several directions.
(EBRT): a  form of radiation therapy in which the radiation is delivered by a machine directed at the area to be radiated as opposed to radiation given within the target tissue such as brachytherapy, see also IMRT