A Comprehensive Cancer Center Designated by the National Cancer Institute

Understanding Clinical Trials

A clinical trial is one of the final stages in the long and carefully planned research process of expanding and improving patient care strategies. Each trial is a study performed on a select group of cancer patients to help researchers determine whether new approaches to cancer prevention, detection, and treatment are safe and effective before they are approved by the Food and Drug Administration (FDA) and administered to patients as a standard therapy.

Clinical trials begin with the development of a protocol (the plan for a trial) to examine promising drugs or procedures. This protocol is developed to answer a few key questions, such as: Does the new treatment being tested work in humans? Is it more effective than the treatment currently being used? Is the new treatment safe? (In other words, do the benefits outweigh the possible risks?)

Answering these questions while exposing as few people as possible to unknown risks often requires a series of clinical trials, typically grouped into "phases." Described in more detail below, these phases range from the assessment of the safety of the drug in a limited number of patients, to initial tests of whether the drug seems to be effective (e.g., provide the expected benefit), to larger trials that more definitively assess whether the new drug or procedure is better than other available options.

Most clinical trials are classified into one of four phases:

Clinical Trial Phases

  1. Phase I trials are the first trials in the clinical trials process. These trials typically determine how often and the method by which a new drug should be administered (orally, injected into the blood stream or muscle, etc.). Phase I trials enroll a small number of patients and focus on safety issues (of the drug, procedure, method of administration, etc.). A frequent endpoint in Phase I trials is determination of the correct dosage of a new drug and determination of its side effects and toxicities.
  2. Phase II trials continue to test the safety of the drug or procedure, but also begin to evaluate how well the new drug works. Phase II studies typically focus on a particular type of cancer and are opened to a larger group of participants.
  3. Phase III trials typically test a new drug or procedure as compared to standard treatments. In most cases, Phase III trials are randomized—that is, participants are randomly assigned, as by the flip of a coin-to receive either the new treatment or the current standard treatment. Phase III trials enroll a larger number of people.
  4. Phase IV trials are used to evaluate the long-term safety and effectiveness of a new treatment. Phase IV trials take place after a treatment has been approved, making it the least common type of clinical trial.

Types of Clinical Trials

There are several different types of clinical trials, each designed to answer different research questions:

Treatment trials help to determine what the most effective treatment is for people living with a specific type of cancer. Many people participate in these trials to help others and contribute to cancer research.

Prevention trials are designed to determine which approaches can best prevent or reduce the risk of developing a specific type of cancer. Prevention trials include both behavioral change studies (such as quitting smoking, changing diet or exercise habits) and studies testing a specific medication or supplement.

Early detection/screening trials help identify methods to detect cancer in people before they develop symptoms. For many cancers, treating the disease at an earlier stage can result in improved outcomes. Trials that screen for cancer include imaging trials, laboratory tests that check blood, urine, or other bodily fluids and tissues, or genetic tests that find inherited genetic markers linked to certain cancers.

Diagnostic trials can help researchers develop new tests or procedures to accurately identify cancer. These trials examine procedures that determine whether cancer is present, where it is located in the body, and if it has spread.

Quality-of-life and supportive care trials are designed to improve the comfort and quality of life of people who have cancer. These trials help people with nutrition problems, infection, nausea, sleeping disorders, depression, or other effects from the disease and its treatment.