What Are the Risk Factors for Breast Cancer?

A risk factor is anything that increases your chance of getting a disease, such as cancer. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for cancers of the lung, mouth, larynx, bladder, kidney, and several other organs.
But having a risk factor, or even several, does not mean that you will get the disease. Most women who have one or more breast cancer risk factors never develop the disease, while many women with breast cancer have no apparent risk factors (other than being a woman and growing older). Even when a woman with breast cancer has a risk factor, there is no way to prove that it actually caused her cancer.
There are different kinds of risk factors. Some factors, like a person's age or race, can't be changed. Others are linked to cancer-causing factors in the environment. Still others are related to personal choices such as smoking, drinking, and diet. Some factors influence risk more than others, and your risk for breast cancer can change over time, due to factors such as aging or lifestyle.

Risk Factors You Cannot Change

Gender: Simply being a woman is the main risk factor for developing breast cancer. Although women have many more breast cells than men, the main reason they develop more breast cancer is because their breast cells are constantly exposed to the growth-promoting effects of the female hormones estrogen and progesterone, thus making breast cancer much more common in women than men. Men can develop breast cancer, but this disease is about 100 times more common among women than men.

Aging: Your risk of developing breast cancer increases as you get older. About 18% of breast cancer diagnoses are among women in their 40s, while about 77% of women with breast cancer are older than 50 when they are diagnosed.

Race: White women are slightly more likely to develop breast cancer than are African-American women. But African-American women are more likely to die of this cancer. Many experts now feel that the main reason for this is because African-American women have more aggressive tumors (see basal-like breast cancer, below). The reasons for this are not known. Asian, Hispanic, and Native American women have a lower risk of developing and dying from breast cancer.