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NCI Dictionary of Cancer Terms

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NCI Dictionary of Cancer Terms



clinical trial phase  listen  (KLIH-nih-kul TRY-ul fayz)

  A part of the clinical research process that answers specific questions about whether treatments that are being studied work and are safe. Phase I trials test the best way to give a new treatment and the best dose. Phase II trials test whether a new treatment has an effect on the disease. Phase III trials compare the results of people taking a new treatment with the results of people taking the standard treatment. Phase IV trials are done using thousands of people after a treatment has been approved and marketed, to check for side effects that were not seen in the phase III trial.