Risk Factors for Breast Cancer

A risk factor is anything that increases your chance of getting a disease, such as cancer. 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.

Gender

Simply being a woman is the main risk factor for developing breast cancer. 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 17% of invasive breast cancer diagnoses are among women in their 40s, while about 78% of women with invasive breast cancer are age 50 or older when they are diagnosed.

Genetic risk factors

Recent studies have shown that about 5% to 10% of breast cancer cases are hereditary as a result of gene changes (called mutations). The most common mutations are those of the BRCA1 and BRCA2 genes. Normally, these genes help to prevent cancer by making proteins that keep cells from growing abnormally. However, if you have inherited either mutated gene from a parent, you are at increased risk for breast cancer.

Family history of breast cancer

Breast cancer risk is higher among women whose close blood relatives have this disease.

Personal history of breast cancer

A woman with cancer in one breast has a 3- to 4-fold increased risk of developing a new cancer in the other breast or in another part of the same breast. This is different from a recurrence (return) of the first cancer.

Race

White women are slightly more likely to develop breast cancer than are African-American women. 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.

Not having children

Women who have had no children or who had their first child after age 30 have a slightly higher breast cancer risk. Having multiple pregnancies and becoming pregnant at an early age reduces breast cancer risk.

Alcohol

Use of alcohol is clearly linked to an increased risk of developing breast cancer. The risk increases with the amount of alcohol consumed. Compared with nondrinkers, women who consume 1 alcoholic drink a day have a very small increase in risk. Those who have 2 to 5 drinks daily have about 1½ times the risk of women who drink no alcohol. Alcohol is also known to increase the risk of developing cancers of the mouth, throat, and esophagus. The American Cancer Society recommends limiting your consumption of alcohol.

Obesity and high-fat diets

Obesity (being overweight) has been found to be a breast cancer risk in all studies, especially for women after menopause. Although your ovaries produce most of your estrogen, fat tissue produces a small amount of estrogen. Having more fat tissue after menopause can increase your estrogen levels and, thereby, increase your likelihood of developing breast cancer.

Physical activity

Evidence is growing that physical activity in the form of exercise reduces breast cancer risk. The only question is how much exercise is needed. In one study from the Women’s Health Initiative (WHI) as little as 1.25 to 2.5 hours per week of brisk walking reduced a woman's risk by 18%. Walking 10 hours a week reduced the risk a little more. The American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Prevention recommend that you engage in 45 to 60 minutes of intentional physical activity 5 or more days a week.

Early detection is important. Find out how to detect breast cancer.