External beam therapy is delivered externally from a machine directed to the cancer inside the patient. Examples of external beam therapy machines include linear accelerators, cobalt machines, or orthovoltage x-ray machines. The type of machine used will be determined by the radiation oncologist. External beam therapy delivers ionizing radiation to the cancer, destroying cancer cells. To give healthy cells time to recuperate, patients receive small doses of radiation at one time, with time enough between treatments.
Most patients receive the radiation treatments on an outpatient basis.
Positioning and actual treatment usually only takes a few minutes. When external beam therapy begins, the technologist closely monitors the patient on a television screen in another room. The patient must lie still on the treatment table during radiation. If the tumor shrinks, the beam of radiation may be adjusted to spare more healthy tissue. This information is not intended to be a substitute for individual medical advice in diagnosing or treating a health problem.