Chemoprevention is the use of natural or synthetic substances to prevent or stop genetic mutations that lead to cancer, or to prevent or stop processes that lead to excessive replication of damaged cells. To identify possible chemopreventive agents (e.g. vitamins, diet, hormone therapy) data obtained from studies of selected groups of people are analyzed and promising compounds are tested in cell culture, animals and further in clinical trials (NCI Chemopreventive Agent Development Research Group).

Currently, approximately 400 compounds are being studied as potential chemopreventive agents, mainly in laboratory research. Over 40 of these compounds are being studied in clinical trials.

• Selective estrogen receptor modulators (SERMS): e.g. tamoxifen, raloxifen (STAR trial), finasteride: Breast and prostate cancer
• Nonsteroidal anti-inflammatory drugs (NSAIDS): aspirin, prioxicam, celecoxib, sulindac: colon cancer, adenomatous polyposis (FAP), esophagus and bladder cancer
• Calcium compounds: Colon cancer
• Glucocorticoids (budesonide): Precancerous changes in lung tissue
• Retinoids (vitamin A and chemical cousins): cancer of cervix, bladder, head, neck, lung and skin
• Vitamins and others: e.g. selenium, vitamin E, 2-difluoromethylornithine (DFMO or eflornithine), folic acid, oltipraz, genistein: cancer of colon and stomach (vitamin C); Colon cancer (Vitamin D); Cancer of lung, head, neck, colon and stomach (vitamin E and beta-carotene); Precancerous cells of the cervix (Folic acid); Skin cancer (Selenium); Breast cancer (monoterpene); Liver cancer (oltipraz); Skin cancer (sunscreen); Head and neck cancer and other (Spirulina fusiform) 

Chemoprevention should not be confused with chemotherapy. Chemotherapy's aim is to kill cells, particularly cancer cells, in the hope of preventing further cancer progression. Chemoprevention, on the other hand, involves administering nontoxic agents to otherwise healthy individuals who may be at increased risk for cancer.

Even though many chemopreventive agents are naturally found in food, they are administered at high doses that can possibly produce unfavorable side effects or present possible detrimental effects. Some of the chemopreventive agents also caused serious side effects (tamoxifen: endometrial cancer and risk of thromboses).




For further informatin visit:
Breast cancer chemoprevention: Medicines that reduce breast cancer risk by the Mayo Clinic
Considerable evidence links dietary factors with cancer risk, but ongoing investigation is needed by Greenwals and McDonald at the Moffitt Cancer Center
Chemoprevention and Breast Cancer by FORCE
Greenwald P. Science, medicine, and the future: Cancer chemoprevention. BMJ 2002;324;714-718