NCI Dictionary of Cancer Terms

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The NCI Dictionary of Cancer Terms features 7,791 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.

photoactivity
(FOH-toh-ak-TIH-vih-tee)
The effect produced when certain substances are exposed to light. In cancer treatment, some drugs become active when exposed to light and are then able to kill tumor cells.