Chemoprevention describes the use of various types of chemical agents to interfere with the development of cancer, either by reversing tumor growth, slowing down the development of malignancy, or by preventing it altogether. These chemical agents come from different sources: some may occur naturally, some may be synthesized, or made, in a laboratory, and others may be derived from a living source, such as a plant or animal.

The changes that cause normal, healthy cells to become cancerous usually occur over a long period of time. Various factors, including genetics, environment, and diet, can lead to damage that in turn causes the abnormal cell structure and uncontrollable growth we call cancer. Not all cancers give rise to early signs; however, some cancers, such as colon cancer, give rise to precancerous growths called polyps, which can be detected and removed before they begin to invade and damage healthy tissue.

Existing cancers are not treated using chemoprevention, since these agents are meant to slow or prevent cancer development. While chemoprevention may delay the processes that cause cells to become cancerous, the possibility still exists that cancer could occur.

As with any kind of treatment, chemopreventive agents may be accompanied by mild to serious side effects. For those with a high risk of cancer, the possibility of slowing or preventing its development may outweigh the risks of unwanted side effects. However, for those individuals with an average risk of developing a particular kind of cancer, it may not be worth the risk. This is why it is always important to discuss all aspects of treatment, including risks and benefits, with your doctor.