If you have been diagnosed with breast cancer, you may be wondering why you got this disease. Unfortunately, it is impossible to say why one woman develops the disease and others do not. About 211,300 women in the United States developed breast cancer in 2003. It is the most common cancer found in women other than skin cancer.
Doctors don't know what causes breast cancer. But by studying large populations of women they have identified many factors that make it somewhat more likely that a woman will develop breast cancer. These are called risk factors, because they raise a person's risk of disease.
A risk factor is not the same thing as a cause. Having a risk factor means a woman is more likely than others to get breast cancer, but it does not mean she will definitely get the disease. Nor does having none of these factors mean a woman is protected from getting breast cancer. The majority of women who develop breast cancer have no risk factors other than the fact that they are women.
A risk factor is usually described in terms of how much it will raise a person's risk of disease above the risk faced by the general population. However, many women read about these factors, misunderstand their impact, and then overestimate their personal risk for disease. In general, it works like this: If a factor is said to raise a person's risk by 20 percent, it increases her risk by an amount equal to 20 percent of her original risk. So if she began with a 10 percent chance of developing the disease, with the added factor she will have a 12 percent chance of disease (20 percent of the original ten percent is 2 percent; 10 plus 2 equals 12). It does not mean that she now has a 20 percent chance of disease. (Keep in mind, too, that you cannot simply add up all your risk factors to determine your probability of disease. The math is a little more complicated.)
Although there is no known way to prevent breast cancer at this time, a woman may be able to lower her risk of disease by controlling some risk factors, such as alcohol intake and exercise.
