What kinds of clinical trials are there
There are many kinds of clinical trials. They range from studies of ways to prevent, detect and diagnose, control and treat cancer, to studies of the psychological impact of the disease and ways to improve the patient's comfort and quality of life (including pain control).
Most cancer clinical trials deal with new treatments. These treatments often involve surgery, radiation therapy (by the use of X-rays or neutrons or other types of cell-destroying radiation), and chemotherapy (by the use of anticancer drugs). Alone, or in combination, these types of treatments can cure cancer patients and prolong the lives of many others. A fairly new area of cancer treatment is biological therapy --- the use of biologicals (substances produced by the body's own cells) and biological response modifiers (substances that affect the body's natural defense systems against disease).
The above information is taken from "What Are Clinical Trials All About?" published by the National Institutes of Health, National Cancer Institute