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Some cancers result from inherited traits. The overwhelming majority of cancers, however, can be prevented. They result from lifestyle choices and controllable environmental factors.

For most of the last 100 years, the dominant theory in cancer research has been that cancer is simply the result of bad luck. Random mutations in DNA result in carcinogenesis, or the inability of a cell to use its normal mechanisms to repair DNA damage when it occurs. Some cancers are heritable, but most cancer, the view used to be, are caused by factors beyond individual control.

Now cancer researchers see the primary causes of cancer as outside the individual, in lifestyle and environment. These factors are not unavoidable or inevitable. Making the right lifestyle choices and living in the right location may be the key to avoiding as many as nine out of ten cases of cancer.

Putting DNA Mutation in Context

The reason researchers used to think that DNA mutations drove cancer is that the more often a cell divides, the more likely it is to undergo DNA mutations. This meshed with the observation that more cancers occur in the elderly, whose cells have replaced themselves many times, and in organs that turn over cells rapidly, such as the colon. Every division of a cell carries the risk of DNA mutations, some of which will cause cancer. Environmental factors, scientists thought, simply are a different way to cause mutated DNA, but the important risk factors were thought to be internal. This would mean that early detection is the most effective strategy against cancer. To be sure, there are some risk factors like hepatitis C for liver cancer and smoking for lung cancer that could be controlled, but for most people, "the Big C has got your number," and only starting treatment as soon as possible after mutations occur can be helpful.

A team at Stony Brook University in New York led by Dr. Yusuf Hannun took a different look at epidemiological data. Hannun and his colleagues noticed that when people moved from places that have low cancer rates to places that have high cancer rates, their rates of cancer increased. They noticed that exposure to UV rays from the sun produces a consistent pattern of mutations in the DNA of the skin that lead to cancer. The effects of radiaiton are not random. They created mathematical models of mutation in breast, prostate, and colon cancer that found that mutations alone are never enough to account for most kinds of cancer. There has to be some kind of outside trigger that accounts for the progression of a cancer cell to a cancerous tumor. If these observations are valid, then cancer prevention is possible.

Naturally, academics debate over which view of cancer is legitimate. There are kinds of cancer that fall more clearly in the "environmental factors" group, such as liver cancer, lung cancer, and basal cell carcinoma, and there are cancers for which there is a clear cancer gene, such as the breast, uterine, and ovarian cancers that can be predicted by BRCA-1 testing. While experts debate over the causes of cancer, it seems only prudent to avoid those things that can give you cancer.

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