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Phase II studies are designed to find out if the treatment actually kills cancer cells in people. Usually groups of 20 to 50 patients with one type of cancer receive a phase II treatment. For example, patients with breast cancer that no longer responds to accepted therapy (it has become resistant to standard therapy) may be treated on a phase II study. Patients are closely observed for anticancer effect by repeated measurement of tumor size to see if it has shrunk since the beginning of the study. When the tumor gets a lot smaller and stays smaller for at least a month, the patient is said to have "responded" to the treatment. If at least one-fifth of the patients in the phase II study respond to treatment, the treatment is judged active against their tumor type. In addition to monitoring patients for response, any side effects of the treatment are carefully recorded and assessed. Since larger numbers of patients receive the treatment in phase II studies than in phase I studies, there is more chance to observe unusual side effects. Each new phase of a clinical trial depends on and builds on information from an earlier phase. If a treatment has shown activity against cancer in a phase II study, it becomes part of a phase III study.
Phase III studies usually compare standard treatments (the treatment most accepted) with treatments that appeared to be good in the small phase II studies. Phase III studies require large numbers of patients; some studies use thousands of patients. Patients are usually randomized, which means they are assigned by chance to one of the treatments being studied. The group that receives the standard treatment is called the "control" group. The researchers know that a certain number of these patients will be helped by the treatment. Another patient group receives the newer therapy to see if it will help the patients more. Phase III studies look for longer life, better quality of life, fewer side effects, and fewer cases of the cancer returning.
information on the Clinical Trails System
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