After promising treatments are explored in animal and/or laboratory studies, researchers perform clinical trials. Once the drug, device, or procedure enters the clinical trials process, it must go through several phases:

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• Phase I trials determine the safety of a new treatment.
• Phase II trials determine whether a certain kind of cancer responds to a new treatment.
• Phase III trials study whether a new treatment is better than standard treatment.
• Phase IV trials find more information about a new treatment that has been already approved for use in patients.