MANY PEOPLE THINK that nothing can be done to avoid cancer. Among experts, however, science historian Robert N. Proctor writes, "Nearly everyone agrees cancer is a preventable disease."

Many researchers believe that at least half the cancer deaths and about two-thirds of the cancer cases in the United States could be prevented. No one can guarantee that he or she will never get cancer, but people can take steps to greatly reduce their cancer risk.

Lifestyle choices

Most methods of reducing cancer risk involve making lifestyle choices that avoid exposure to carcinogens. Chief among these choices is not using tobacco. Those who have started smoking should do their best to quit. People should avoid secondhand smoke whenever possible as well. Tobacco in other forms, such as chewed (smokeless) tobacco, is also dangerous. If everyone gave up tobacco use...