Design and Phases of Clinical Trials

Clinical trials are designed using experimental standardized plans, which sometimes can be very complex. These standardized plans, called "protocols," are developed as part of every clinical trial and provide a framework for the objective collection and analysis of data, and the protection of study volunteers. The development of clinical trial protocols is initially based on laboratory and animal research, and sometimes on other clinical trials involving human beings. In the case of an experimental treatment for a disease, the protocol would identify exactly what procedures would be followed to determine effectiveness against a specific disease and any side effects that occur. Oncologists and oncology nurses (doctors and nurses specializing in cancer, respectively) follow the protocols in order to accurately collect data for research.

Before a clinical trial can begin, a scientific and ethical review board, called an Institutional Review Board (IRB), evaluates the proposed clinical trial protocol to determine whether it is safe, scientifically sound, and appropriately designed, and also to ensure that patients are appropriately protected. This board is made up of health care professionals, administrators, and lay persons. All clinical trials using drugs, devices, or procedures not yet licensed by the FDA must receive the approval of the appropriate IRB before any patients are allowed to volunteer for participation.


All clinical trials of investigational agents are divided into four categories: Phase I, Phase II, Phase III, and Phase IV. All experimental cancer treatments must go through the first three phases before being submitted to the FDA.

  • In Phase I, researchers determine the safe dose of the experimental agent and learn about its side effects. Patients with many different types of cancer may be asked to take part in a Phase I trial. Patients are usually divided into distinct groups. Each group is given different doses of the experimental agent so that safe doses can be found, most importantly, the highest dose of the drug that can be given safely to human beings.
  • In Phase II, researchers test the effectiveness of the experimental agent in stopping or controlling the growth of tumor cells for a specific type of cancer.
  • In Phase III, researchers determine how the experimental agent compares with standard treatment in the management of tumors. To gather as much information as possible, Phase III trials usually involve many more patients than the previous phases and often are performed simultaneously at many cancer research centers.
  • In Phase IV, researchers study drugs and/or treatments that have already received FDA approval. The goal of Phase IV trials is to study how safe and effective a drug or procedure is over time.

All patients taking part in a clinical trial are followed carefully by their doctor and nurse. Physical examinations, blood tests, and x-ray examinations all may be part of your evaluation before, during, and after each trial. These examinations and tests are done to determine whether you are an appropriate volunteer for a clinical trial, to measure the effectiveness of the experimental agent, and to help detect side effects as early as possible.

Your role in a clinical trial may alter or cease for a variety of reasons. Some clinical trials stop after a predetermined length of time. If your disease changes for the better or worse, or if side effects become too severe, it may be determined that it would be better for you to stop or alter your dose. If you or your doctor feel at any time that a clinical trial is no longer your best option, or it is felt that another treatment would be more beneficial, you may stop. If your participation in a clinical trial is stopped for whatever reason, you still may be evaluated to see if an approved or standard treatment is available, or if another clinical trial would be an appropriate option.