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The Sidney Kimmel Comprehensive Cancer Center

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Understanding Clinical Trials

Why are there clinical trials?

A clinical trial is one of the final stages of the cancer research process.  Studies are done with cancer patients to find out whether promising approaches to cancer prevention, diagnosis, and treatment are safe and effective.

What are the different types of clinical trials?

  • Treatment trials test new treatments (like a new cancer drug , new approaches to surgery or radiation therapy, new combination of treatments, or new methods such as gene therapy ).
  • Prevention trials test new approaches (such as medicines, vitamins, minerals, or other supplements) that physicians believe may lower the risk of certain types of cancer.  These trials look for the best way to prevent cancer in people who have never had cancer or to prevent cancer from coming back or a new cancer from occurring in people who already have cancer.
  • Screening trials test the best way to find cancer, especially in its early stages.
  • Quality of Life trials explore new ways to improve comfort and quality of life for cancer patients

What are the phases of clinical trials?

  • Phase I Trials:  These first studies in people evaluate how a new drug should be given (ie: by mouth, injected into the blood, or injected into the muscle), how often, and what dose is safe.  A phase I trial usually enrolls only a small number of patients, sometimes as few as a dozen.
  • Phase II Trials:  A phase II trial continues to test the safety of the drug, and begins to evaluate how well the new drug works.  Phase II trials usually focus on a particular type of cancer. 
  • Phase III Trials:  These studies test a new drug, a new combination of drugs, or a new surgical procedure in comparison to the current standard.  A person is usually assigned to the standard group or the new group at random (called randomization).  Phase III trials often enroll large numbers of people and may be conducted at  many physicians' offices, clinics, and cancer centers nationwide.

    In addition, after a treatment has been APPROVED and is being marketed, the drug's maker may study it further in
  • Phase IV Trials:  The purpose of the phase IV trial is to evaluate the side effects, risks, and benefits of a drug over a longer period of time and in a larger amount of people than in phase III clinical trials.  Thousands of people are involved in a phase IV trial.