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Home > Resources > PAF Publications > PAF Guides & Major Publications > A Guide to Clinical Trials > What is a Clinical Trial?

What Is A Clinical Trial?

A Clinical Trial is a study of new drugs, combinations of drugs (some already FDA approved for other purposes) and/or treatments to see how well they work – especially when compared with current standard of care treatment. Each study has rules about who can and cannot participate such as age, sex or stage of disease. "Clinical trials have protocols, or action plans, for conducting a trial. This helps the participant understand what will be done, how it will be done and why each part is needed. In the United States, an independent committee of physicians (Institutional Review Board), statisticians and members of the community must approve and monitor the protocol. They make sure that the risks are small and are worth the potential benefits."1

Each trial lists eligibility criteria for participation. For example, there are studies that need volunteers with a certain disease while others are looking for healthy people. Some trials want all female while others want all male participants. The sponsor of the study writes the protocol, which explains what the trial will do, how the trial will be conducted, location of the study, eligibility criteria, and how and when the participants will be evaluated. There are many sponsors of clinical trials. The National Cancer Institute has a webpage for locating clinical trials as well as a patient recruitment line to screen potential patients. Other sponsors include physicians, single institution, the Department of Defense, the Department of Veterans Affairs, and/or biopharmaceutical manufacturers.

Clinical trials are done to gather information for many purposes. The purpose of the trial defines how it will be conducted. The different types of trials include:

  • Treatment trials test experimental treatments, new combinations of drugs, and new approaches to surgery or radiation therapy.
  • Prevention trials look for better ways to prevent disease in people who have never had the disease or to prevent a disease from returning. Approaches may include medicines, vaccines, vitamins, minerals, or lifestyle changes.
  • Diagnostic trials are conducted to find better tests or procedures for diagnosing a particular disease or condition.
  • Screening trials test the best way to detect certain diseases or health conditions.
  • Quality of Life trials (or Supportive Care trials) explore ways to improve comfort and the quality of life for individuals with a chronic illness.1

What are the phases of clinical trials?

Clinical trial phases are designed to test the new treatments being proposed. Phases of clinical trials go from phase 1 through phase 4. As results are obtained, the trial moves to the next phase. There are 4 phases.

Phase 1: When a drug or treatment is in a Phase 1 trial, the researchers are studying to determine how the drug or treatment will be administered (by mouth, through the vein (IV), etc). The researchers are looking for the proper dose and monitoring for side effects. The study focuses on a small group of participants.

Phase 2:When a drug or treatment advances to a Phase 2 trial, the researchers are studying the results to determine the effectiveness of the drug or treatment. Phase 2 trials collect information on the safety and benefit of the treatment. The study expands to 100 or more participants.

Phase 3:When a drug or treatment advances to a Phase 3 trial, the researchers are studying to determine if one treatment is better than another. The trial agent is studied in comparison to current standard of care treatment. Phase 3 trials expand in size to several hundred to thousands of participants.

Phase 4:When a drug or treatment advances to a Phase 4 trial, the researchers are monitoring long-term safety and effectiveness of the treatment. These are also known as Post Marketing Surveillance Studies.2

As a drug or treatment advances in each Phase of a clinical trial the number of institutions, or facilities, offering the trial increases. Major medical centers across the nation participate in Phase 2, 3 and 4 trials. In some situations, it may be possible for you to enroll in a clinical trial at a local facility.

In the United States, the FDA (Food and Drug Administration) requires all new drugs or treatments complete multiple years of testing before approving them for use as standard of care. All current drugs have been through Clinical Trial testing at some point to achieve the standard of care label from the FDA. Some consider clinical trials the most advanced cancer treatment therapy we have. Making the decision to enroll in a clinical trial is a personal one. Because of advances in medical science, clinical trials can offer you a chance to participate in cutting edge treatments, before they are available to the general public.


1Medline Plus, Clinical Trials. Retrieved 2/25/2009 from http://www.nlm.nih.gov/medlineplus/clinicaltrials.html

2Understanding Clinical Trials, retrieved 2/28/2009 from http://clinicaltrials.gov/ct2/info/understand


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