Clinical trials are research studies designed to find new and potentially better ways to treat patients who have cancer and other diseases. They are done to determine whether a newly developed treatment is safe and effective, how and at what dose the new treatment is best administered, and whether the treatment is better than other options.
Clinical trials may test new drugs, new approaches to using existing treatments, or newly developed treatment methods. They are unique studies in that they rely on patients’ participation to test the new therapies. The standard treatments of today were once studied in clinical trials. Clinical trials are conducted only after a long process of research on the new treatment has already been completed.
When planning a clinical trial, an investigator (usually a physician) must write a detailed plan or protocol that outlines the study’s background and purposes, how it will be conducted, the types of patients who may participate, schedules, what drugs will be involved and in what amounts, and how long the study will take. This ensures that participants receive appropriate treatment and high-quality care and that the research is conducted scientifically.
All volunteers, researchers, doctors and other health professionals who participate in or manage a clinical trial must follow the FDA’s strict rules and regulations, ensuring that all participants are treated as safely as possible. Some clinical trials may be blinded, meaning the patients or both the patients and their doctors do not know which treatment is being given. When effective treatment is available, it is unethical for patients to be given a placebo. For example, a cancer clinical trial would study the effectiveness of a new treatment option against the current standard of care.
Clinical trials must go through three phases:
Phase I Trials
Phase I trials evaluate how a new drug should be given (for example, by mouth or injection), how often, and in what dose. They begin after a treatment is approved for human testing, so only a small number of participants are admitted, usually 20-80 people.
Phase II Trials
This kind of trial continues to test the drug’s safety and begins to evaluate how well the new drug works. Phase II studies usually focus on a particular type of cancer or disease. Like Phase I trials, they often include a limited number of participants, around 100-300 people.
Phase III Trials
Phase III trials compare a new drug or treatment with standard or similar treatments and test it for effectiveness, side effects and safety. Approximately 1,000-3,000 participants are randomly assigned to either the standard or the new treatment group. Often the data from phase III trials are sent to the FDA for further review and to determine if a new therapy should be approved to be a future standard treatment.
Beyond Clinical Trials
The final stage, Phase IV, occurs after the new drug is approved by the FDA and made available to the public. At this point, researchers continue to monitor the drug’s safety in the general population and gather more information about the drug or treatment’s benefits and how it can best be used.
The National Institutes of Health (NIH) and the U.S. Food & Drug Administration (FDA) are great resources for learning more about clinical trials.
More to Read
- Women and Clinical Trials: Closing the Gaps
- UM Greenebaum Cancer Center Clinical Trials Database
- Enrolling in a Clinical Trial
- Research at UM School of Medicine
Medically reviewed by Ranee Mehra, MD.
Updated March 7, 2025
