Clinical trials are research studies conducted with people.
There are many types of clinical trials. They include studies to prevent, detect, diagnose, and treat a disease as well as studies of the psychological impact of the disease and ways to improve a participant's comfort and quality of life. Chemoprevention trials, one type of clinical trial, look at possible ways to prevent cancer using drugs, vitamins, or other agents. The PCPT is the largest chemoprevention trial ever done with men. SWOG is a cooperative group of cancer researchers from medical centers around the country.