Clinical Trial Definitions


A clinical trial is a research study that finds new ways to prevent, diagnose or treat disease. Cancer clinical trials test new treatments in people with cancer. These treatments investigate promising new drugs, drug combinations, new approaches to surgery or radiation therapy, and advances in new areas such as gene therapy. Clinical trials are the final step in a long process. 


Testing of a new cancer drug or treatment is done in an orderly series of steps called phases. This allows researchers to obtain reliable information about the drug or treatment in order to protect patients in each phase of the study.

  • Phase 1 trials: Researchers test a new drug or treatment in a small group of people for the first time to evaluate its safety, determine a safe dosage range and identify side effects.
  • Phase 2 trials: This phase's focus is on safety and whether the drug or treatment works in people who have a certain disease or condition. For example, participants receiving the new drug or treatment may be compared with similar participants receiving a different drug or treatment.
  • Phase 3 trials: In this phase the drug or treatment is given to a large group of people to confirm effectiveness, monitor side effects, compare to commonly used drugs or treatments and collect information that will allow the drug or treatment to be used safely.
  • Phase 4 trials: Phase 4 studies are conducted after a drug or treatment has been approved for use in the general public. These studies are used to provide more information about side effects; what the long term risks and benefits are; and how well the drug or treatment works when it’s used more widely.