The Phases of Clinical Trials

The development of new cancer treatments evolve through several orderly steps (phases). Each phase is designed to answer specific questions about safety, risks, and effectiveness compared to standard treatment.

Phase I Trials: Is it safe?
These trials usually include a small number of patients whose treatment options are limited but may benefit from the drug. The primary goals for conducting the trial is to determine the maximum tolerated dose that can be safely given without serious side effects and how the drug works in the human body. Results from phase I trials are used to begin phase II trials.

Phase II Trials: Does it work?
If the new drug is determined to be reasonably safe in phase I trials, phase II trials are initiated. These trials usually focus on a particular type of cancer and are designed to determine the effectiveness of the new drug, using the dose and method determined in the phase I trial. A larger number of patients are planned for this phase and the less common side effects may be observed. If results from the phase II trial prove to be beneficial to the patient, the new drug is considered active against cancer. The new drug may be FDA approved as standard treatment at this phase or may continue to be evaluated for effectiveness in a phase III trial.

Phase III Trials: Does it work better than standard treatment?
Usually phase II trials, showing evidence of benefit, must undergo one more phase before obtaining FDA approval. Phase III trials compare safety and effectiveness of the new drug to the standard of treatment in a controlled environment. Because it is unknown which treatment is better, patients are chosen at random to receive either the standard treatment or the new treatment. These trials include a large number of patients (at least several hundred) and are generally conducted throughout the country or world-wide to validate effectiveness.

Phase IV Trials: Are there more questions?
After a drug has been approved by the FDA for standard treatment, the manufacturer of the drug may continue to evaluate its effectiveness, safety, risks, and benefits. Thousands of patients are usually included in this phase over a long period of time to gain better knowledge of the full effects. This additional information may not be critical to FDA approval for public use.