What Is the Purpose of Clinical Trials?

The goals of different phases of clinical trials

What is the purpose of clinical trials and what do you need to know if you are considering one of these studies? Clinical trials are surrounded in a bit of mystery, and many people become anxious about enrolling.

Learn about the different types of trials, the goals of phase 1, phase 2, phase 3, and phase 4 trials, and how clinical trials are changing with advances in targeted therapies and immunotherapy so that sometimes an early stage clinical trial may be the best option for survival.

Scientist pipetting samples into eppendorf tubes
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Overall Purpose of Clinical Trials

The purpose of clinical trials is to find ways to more effectively prevent, diagnose, or treat disease. Every medication, vaccine, and procedure that is used in modern medicine was once studied as a part of a clinical trial.

Myths about clinical trials abound—such as you will be essentially a human guinea pig. But it can be helpful to understand that any approved treatment you will receive as a standard of care was once studied in a clinical trial and found to be superior or have fewer side effects than whatever had been used prior to that time.

Types of Clinical Trials

The purpose of different trials varies depending on the question that is being asked as part of the study. Different types of clinical trials include:

  • Preventive trials: These trials study ways to prevent a disease or a complication of a disease from occurring.
  • Screening trials: Screening trials look for ways to detect a disease at an earlier, more treatable stage. For example, trying to find a way to detect lung cancer at an earlier stage than it is usually diagnosed. They are also called early detection trials.
  • Diagnostic trials: These trials look for better and less invasive ways to diagnose a disease.
  • Treatment trials: People are often most familiar with treatment trials, the studies that look for medications and procedures that work better or are tolerated better with fewer side effects.
  • Quality of life trials: Trials looking for better ways of providing supportive care for people with a disease are very important and becoming more common.

Phases of Clinical Trials

In addition to being a study of a certain type, clinical trials are broken down into phases including:

  • Phase 1 trials: These trials are conducted on a small number of people and are designed to see if a treatment is safe, and what side effects it may have.
  • Phase 2 trials: After a treatment is considered to be relatively safe, it is evaluated in a larger group in a phase 2 trial to see if it is effective.
  • Phase 3 trials: If a treatment is found to be relatively safe and effective, it is then evaluated in an even larger phase 3 trial to see if it is more effective than standard treatments available, or has fewer side effects than standard treatments. If a treatment is found to be more effective or safer in a phase 3 trial, it may then be evaluated for FDA approval.
  • Phase 4 trials: Usually a treatment is approved (or not approved) by the FDA on completion of a phase 3 trial. Phase 4 trials are done after FDA approval mainly to see if side effects occur over time in people who are using the treatment. These trials are also called “postmarketing surveillance.”

Need for Clinical Trial Participation

Not only are clinical trials able to move medicine forward, but in some cases, experimental treatments can offer a chance of survival for patients who haven’t responded to established treatments. Even so, it isn’t always easy to recruit enough participants for trials. In the case of cancer trials, fewer than 5% of adults with cancer enroll in cancer clinical trials.

If you have a condition that’s challenging to treat, talk to your healthcare provider about whether there might be clinical trials recruiting participants for your condition.

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2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institutes of Health. NIH clinical research trials and you: the basics.

  2. Unger JM, Cook E, Tai E, Bleyer A. The role of clinical trial participation in cancer research: barriers, evidence, and strategies. Am Soc Clin Oncol Educ Book. 2016;36:185-198. doi:10.1200/EDBK_156686