Clinical trials are designed to answer questions about treatment of various types of cancer. Trials can either be in-house, where the trial takes place in a single institution, or multi-institutional, where multiple cancer treatment facilities participate in the study. The most common types of clinical trials are multi-institutional trials because it often takes too much time to accrue a sufficient number of patients in a trial to design it as a single-institution study. However, the advantage of a single-institution study is that there tends to be less variability in treatment technique, which can affect the outcome.

Clinical trials for cancer patients may be phase I, II, or III. In a phase I or phase II trial, the patient participates in an investigational type of treatment but is not randomly assigned to participate in one of two or more different treatments. Phase I trials usually are done to determine the safe dose of a new treatment drug or regimen. A phase II trial is designed to determine in a small group of patients whether a new treatment is effective in treating a certain disease. In a phase III trial, the patient is randomized (randomly assigned, by chance, similar to the toss of a coin; usually done by computer) to one of two or more different treatments, or “treatment arms,” that the study is designed to compare. For example, the comparison may be between a standard treatment and a new treatment, or between a single treatment modality and a combination therapy. Usually a phase III trial includes a larger number of patients. For the patient and physician to participate in a phase III trial, it is necessary that the physician does not have any strong supposition as to which of the treatment arms might be more advantageous. Controlled clinical trials are critical to answering many of the important treatment questions that exist today and will arise in the future.