NCI Dictionary of Cancer Terms
The NCI Dictionary of Cancer Terms features 7,847 terms related to cancer and medicine.
Browse the dictionary by selecting a letter of the alphabet or by entering a cancer-related word or phrase in the search box.
- listen (ih-RAY-dee-AY-shun)
The use of
high-energy radiation from x-rays, gamma rays, neutrons,
protons, and other sources to kill cancer cells and shrink
tumors. Radiation may come from a machine outside the body
(external-beam radiation therapy), or it may come from
radioactive material placed in the body near cancer cells
(internal radiation therapy). Systemic
irradiation uses a radioactive substance,
such as a radiolabeled monoclonal antibody, that travels in
the blood to tissues throughout the body. Also called radiation therapy and radiotherapy.