There are several directions of eliminating cancer as a major health problem. One of the most important and promising of these directions is cancer prevention. Although the certain cause of cancer is not known yet, some of the risk increasing factors are clarified. Knowing cancer risk increasing factors helps scientists and health professionals elaborate a specific plan of prophylactic actions for high-risk individuals. Depending on the predominant risk factor, cancer prevention can be different.
Cancer prevention may include alimentary prevention (for example, consuming more fruit and vegetables and less saturate fats), lifestyle changing (quit smoking, more physical activity), chemoprevention agents (tamoxifen, cis-retinoic acid), and surgery (bilateral mastectomy in women with BRCA1 gene mutation). Chemoprevention agents have not been studied enough yet, but they already seem to be very promising.
Chemo-prevention agents are natural or synthetic substances that are used for cancer prevention in high-risk individuals. They can intervene at two different levels: either prevent/stop genetic mutations (genes level) or prevent/stop excessive replication of damaged cells (cellular level). The principal classes of chemoprevention agents are antiproliferative agents (cis-retinoic acid), antioxidants (vitamins A, E, C), antimutagens (oltipraz), non-steroidal anti-inflammatory drugs (sulindac, aspirin, ibuprofen), and estrogen receptor modulator (tamoxifen).
Each of these agents may be used for the prevention of certain types of cancer. For example, tamoxifen is used preponderantly for breast cancer prevention. Chemo-prevention is often confused with chemotherapy, which is not the same. Chemotherapy is used for slowing of inhibiting cancer evolution in patients who have cancer. Chemo-prevention is used to prevent cancer initiation in patients who do not have an active cancer.
Considering the fact that chemoprevention supposes taking medicines for long periods of time (for example, tamoxifen is taken for up to 5 consecutive years) all the chemoprevention agents must respond to specific requests. First of all, their effectiveness must be scientifically proven. They must have low costs and be accessible for a wide range of population, and also have minimal side effects. Chemo-prevention agents are not studied sufficient yet, and can be quite dangerous if used irrationally. For example, there are studies that show that the use of beta-carotene (the precursor of vitamin A) for the prevention of lung cancer produced 18% lung cancer risk increase in trial group.
That is why any chemoprevention agent must go through three phases before it can be accepted and administered to general population. All three phases involve from 25 to 10 000 volunteers and study effectiveness, toxicity, short-time and long-time side effects. Although chemo-prevention agents haven't been studied enough yet, chemo-prevention is an important and promising direction of cancer prevention.