PHASE I: Determines the maximum tolerated dose and dosing schedule of a drug, how it works, and its toxicity. The trial includes a small number of patients whose cancer has come back or does not respond to standard treatment. The trial includes patients with different cancers.
PHASE II: Determines how the drug affects the cancer, and evaluates toxicity. The trial includes groups of patients with the same cancer.
PHASE III: Determines how the drug/treatment works by assessing survival and time to progression of the disease, and obtains information about quality of life. The trial includes large numbers of patients, and randomly assigns the patients to the experimental treatment or the standard therapy.
PHASE IV: Expands "off-label" use of the drug, meaning the drug may be used for a disease it was not originally approved for. The trial also continues to assess toxicity.