Clinical trials are carried out in phases, each designed to find out certain information. Patients may be eligible for studies in different phases depending on their general condition and the type and stage of their illness.
In a Phase I study, a new research treatment is given to a small number of patients. The researchers must find the best way to give a new treatment and how much of it can be given safely, watching carefully for any harmful side effects. By this point, the research treatment has been well-tested in laboratory and animal studies, but very little information is available how human patients will respond.
Phase II studies determine the effect of a research treatment on various types of illnesses. Each new phase of a clinical trial depends on and builds on information from an earlier phase. If a treatment has shown activity against a particular illness in Phase II, it moves to Phase III. Here it is compared to the standard method of treatment to see which is more effective.
Often researchers use standard therapy as the base to design new and hopefully better treatments. Then in Phase III, the new treatment is directly compared to the standard treatment. In Phase IV studies, the new research treatment becomes part of standard treatment in patient care.
If you agree to take part, you will be asked to sign a form, called an informed patient consent. Before you sign, ask the doctor or nurse to explain any part(s) of the form or the trial that are unclear to you.