Clinical Trials at Duke Comprehensive Cancer Institute

What are the phases of a clinical trials?

Most clinical research that involves the testing of a new drug progresses in an orderly series of steps, called phases. This allows researchers to ask and answer questions in a way that results in reliable information about the drug and protects the patients. Clinical trials are usually classified into one of three phases:

1. Phase I trials are the first step in testing a new treatment in humans. In these studies, researchers evaluate how a new drug should be given (by mouth, injected into the blood, or injected into the muscle), how often, and what dose is safe. A Phase I trial usually enrolls only a small number of patients, sometimes as few as a dozen.

2. Phase II trials focus on evaluating how well the new drug works, as well as continue to test the safety of the drug. Phase II studies usually focus on a particular type of cancer.

3. Phase III trials compare the results of people taking the new treatment with results of people taking standard treatment. A participant will usually be assigned to the standard treatment group or the new treatment group at random (called randomization). Phase III trials often enroll large numbers of people and may be conducted at many doctors' offices, clinics, and cancer institute nationwide.