Scientific research has shown that cancer is not usually caused by a single catastrophic event, but rather is the result of a process that may take decades to culminate in disease.  Because of the slowness of this process, there is opportunity to intervene to stop or reverse the process.  Clinical trials for cancer prevention seek to take advantage of this time by identifying at-risk people, define methods to prevent or reduce their risk, detect cancer in its earliest stages and actively prevent cancer invasion.

Clinical progress in this area has been seen with the use of tamoxifen for breast cancer prevention; the use of the arthritis/anti-inflammatory drug celecoxcib to reduce the development of polyps in familial adenomatous polyposis (FAP); and the use of low-dose aspirin for colon cancer reduction in patients with a history of colon polyps.  For more prevention information, see www.cancer.gov.