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.

historical control subject
(hih-STOR-ih-kul kun-TROLE SUB-jekt)
An individual treated in the past and used in a comparison group when researchers analyze the results of a clinical study that had no control group. The use of a control, or comparison, group helps researchers determine the effects of a new treatment more accurately.