NCI Dictionary of Cancer Terms

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The NCI Dictionary of Cancer Terms features 7,800 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.

high-energy photon therapy
(hy-EH-ner-jee FOH-ton THAYR-uh-pee)
A type of radiation therapy that uses high-energy photons (units of light energy). High-energy photons penetrate deeply into tissues to reach tumors while giving less radiation to superficial tissues such as the skin.