Types of Trials

Prevention trials test new approaches such as medications, vitamins, or other supplements that doctors believe may lower the risk of developing a certain type of cancer. Most prevention trials are conducted with healthy people who have not had cancer. Some trials are conducted with people who have had cancer and want to prevent recurrence (return of cancer) or who want to reduce the chance of developing a new type of cancer.

Screening trials study ways to detect cancer earlier. They are often conducted to determine whether finding cancer before it causes symptoms decreases the chance of dying from the disease. These trials involve people who do not have any symptoms of cancer.

Diagnostic trials study tests or procedures that could be used to identify cancer more accurately. Diagnostic trials usually include people who have signs or symptoms of cancer.

Treatment trials are conducted with people who have cancer. They are designed to answer specific questions about, and evaluate the effectiveness of, a new treatment or a new way of using a standard treatment. These trials test many types of treatments such as new drugs, vaccines, new approaches to surgery or radiation therapy, or new combinations of treatments.

Quality-of-life (also called supportive care) trials explore ways to improve the comfort and quality of life of cancer patients and cancer survivors. These trials may study ways to help people who are experiencing nausea, vomiting, sleep disorders, depression, or other effects from cancer or its treatment.

Genetics studies are sometimes part of another cancer clinical trial. The genetics component of the trial may focus on how genetic makeup can affect detection, diagnosis, or response to cancer treatment.

Population- and family-based genetic research studies differ from traditional cancer clinical trials. In these studies, researchers look at tissue or blood samples, generally from families or large groups of people, to find genetic changes that are associated with cancer. People who participate in genetics studies may or may not have cancer, depending on the study. The goal of these studies is to help understand the role of genes in cancer's development.


Phases of Trials

Phase I clinical trials are first-time tests of drugs or treatments on human patients. Though the drug or treatment has not yet been tested on people, researchers have reason to believe it will be beneficial. At this stage, researchers do not know the drug's effectiveness, the best dose to administer, or what side effects may occur. A suggested starting dose for humans is found through laboratory experiments. All patients involved in Phase I clinical trials receive a form of treatment for their cancer; none are administered placebos (medically inactive agents sometimes used in medical research for comparison purposes.)

Phase II clinical trials begin once an appropriate dosage of the drug is defined through Phase I trials. In this stage of testing, researchers will determine the drug's effectiveness in treating a specific kind and stage of cancer. As in Phase I clinical trials, all patients involved in Phase II clinical trials receive active treatment; none are administered placebos.

Phase III clinical trials test therapies that have proven to be effective in the first two stages of testing. Phase III clinical trials put the new (investigational) therapy in perspective. For example, a phase III trial may compare the current standard therapy against the new investigational therapy. Or, it may compare patients given the investigational therapy and standard therapy with those who are administered only the standard therapy. Patients participating in Phase III trials are randomly assigned to one of the treatments in the study. This means a patient is selected by chance to be in one treatment group or another. This randomization is essential to allow investigators to determine which therapy is truly more effective. While Phase I and Phase II trials may involve a few dozen patients, Phase III trials can include hundreds of patients.

Phase IV trials are conducted to further evaluate the long-term safety and effectiveness of a treatment. They usually take place after the treatment has been approved for standard use. Several hundred to several thousand people may take part in a phase IV study. These studies are less common than phase I, II, or III trials.