Cancer clinical trials are research studies that test the safety and effectiveness of potential new treatments and diagnostic or prevention strategies. Patients volunteer to take a new drug or try a new treatment to help scientists answer important treatment-related questions.
Each treatment must be tested in multiple clinical trials. These trials become more complex as researchers learn more about the treatment.
First, researchers must show the treatment is safe. Then they must show it works as intended. Then they compare it to existing treatments. If a drug or other type of therapy succeeds in all these tests, the Food and Drug Administration (FDA) may approve it for widespread use.
What Are the Phases of Cancer Clinical Trials?
Each phase of a trial has a different purpose. Each phase also helps researchers answer different questions.
Phase 1: Safety
This is the first time a treatment is tested in humans. However, to get to this phase, the treatment must have already performed well in laboratory and animal testing.
The main goal of a Phase 1 trial is to find out whether the treatment is safe. Researchers also search for the largest dose people can take without serious side effects. In most instances, researchers slowly escalate the dose of the drug until they reach the largest tolerated dose that is likely to show the most clinical benefit in later phases. Phase 1 clinical trials typically include 15 to 50 patients — far fewer than later phases.
Phase 2: Effectiveness
If the treatment proves to be safe during Phase 1, it then moves to Phase 2 testing. During Phase 2, the main goal is to determine whether the treatment works (also known as efficacy) against cancer.
Researchers give patients the highest dose they can tolerate safely as determined in the Phase 1 study. Then they watch patients to see what effects the treatment has on the cancer. They also continue to watch for safety.
Phase 2 trials involve more people — usually 25 to 100 patients. Possible results of a Phase 2 trial could be that the tumor shrinks or stops growing. Others include extending survival time or improving quality of life.
Phase 3: Comparison
If Phase 2 trials show the new treatment to be effective, it is then compared with an existing treatment in a head-to-head Phase 3 trial. Thousands of cancer patients may take part in these larger trials. A Phase 3 trial is the last step before the FDA decides whether to approve the treatment for use in the United States.
In Phase 3 trials, researchers might use a computer program to randomly assign patients to receive either the new treatment or the existing treatment.
When possible, researchers don’t know which patients receive which treatment. This is called a double-blind study. It helps ensure that trial results remain free from bias toward one treatment or the other.
As in earlier stage trials, safety continues to be a focus in Phase 3.
Phase 4: Other uses or benefits
Even after the FDA approves a new treatment, researchers may continue to study it. They want to be sure the treatment continues to be safe. They also may want to find other uses for the new treatment.
For example, the treatment may be effective against a different type of cancer than the one approved by the FDA, but it must be proven. Because the treatment is already on the market, Phase 4 trials use many thousands of patients.
Researchers sometimes design clinical trials that combine Phase 1 and 2, or Phase 2 and 3, in a single trial to answer questions faster or with fewer patients.
What Are the Types of Cancer Clinical Trials?
Treatment trials are the best known type of clinical trials. They test new treatments, drug combinations, or approaches to surgery or radiation therapy. But scientists use other types of clinical trials, too.
The National Institutes of Health reports that each type of trial can reveal important information about people with cancer. Other types of clinical trials include:
- Prevention trials: How can we prevent cancer in the first place? How can we prevent cancer from returning? Depending on the type of cancer, researchers may study medicines, vaccines, or lifestyle changes.
- Screening trials: How can we detect cancer earlier, when it is more likely to be curable?
- Diagnostic trials: How do we know we’re using the most effective tests or procedures to diagnose a particular type of cancer?
- Behavioral trials: What are the most effective ways to promote healthy behaviors that may help prevent cancer?
- Quality of life trials: How can we improve quality of life for people with cancer? These are also known as supportive care trials.
Researchers choose the type of clinical trial based on the question they want to answer.
People with cancer benefit when they choose a health care institution that offers a wide variety of clinical trials. At UPMC Hillman Cancer Center, researchers take part in more than 450 cancer clinical trials each year.