Risk Factors for Breast Cancer

In 1940, the lifetime risk of a woman developing breast cancer was 5%, or one in 20. The American Cancer Society estimates that risk to be 13% in 2009, or almost one in eight. In many cases, it's not known why a woman gets breast cancer. In fact, 75% of all women with breast cancer have no known risk factors.

What Are the Risk Factors of Breast Cancer?

A risk factor is anything that increases a person's chance of getting a disease. Different cancers have different risk factors.

But having a cancer risk factor, or even several of them, does not necessarily mean that a person will get cancer. Some women with one or more breast cancer risk factors never develop it, while most women with breast cancer have no apparent risk factors.

Significantly higher risk

A woman with a history of cancer in one breast has a 3- to 4-fold increased risk of developing a new breast cancer, unrelated to the first one, in the other breast or in another part of the same breast. This is different than a recurrence of the previous breast cancer.

Moderately higher risk

• Getting older. Your risk for breast cancer increases as you age. About 77% of women diagnosed with breast cancer each year are over age 50, and almost half are age 65 and older. Consider this: In women 40 to 49 years of age, there is a one in 68 risk of developing breast cancer. In the 50 to 59 age group, that risk increases to one in 37.
• Direct family history. Having a mother, sister, or daughter ("first degree" relative) who has breast cancer puts you at higher risk for the disease. The risk is even greater if your relative developed breast cancer before menopause and had cancer in both breasts. Having one first-degree relative with breast cancer approximately doubles a woman's risk, and having two first-degree relatives increases her risk 5-fold. Having a male blood relative with breast cancer will also increase a woman's risk of the disease.
• Genetics. Carriers of alterations in either of two familial breast cancer genes called BRCA1 or BRCA2 are at higher risk. Women with an inherited alteration in either of these genes have up to an 80% chance of developing breast cancer in their lifetime.
• Breast lesions. A previous breast biopsy result of atypical hyperplasia (lobular or ductal) increases a woman's breast cancer risk by four to five times.

Slightly higher risk

• Distant family history. This refers to breast cancer in more distant relatives such as aunts, grandmothers, and cousins.
• Previous abnormal breast biopsy. Women with earlier biopsies showing any of the following have a slight increased risk: fibroadenomas with complex features, hyperplasia without atypia, sclerosing adenosis, and solitary papilloma.
• Age at childbirth. Having your first child after age 35 or never having children puts you at higher risk.
• Early menstruation. Your risk increases if you got your period before age 12.
• Late menopause. If you begin menopause after age 55, your risk increases.
• Weight. Being overweight (especially in the waist), with excess caloric and fat intake, increases your risk, especially after menopause.
• Excessive radiation. This is especially true for women who were given radiation for postpartum mastitis, received prolonged fluoroscopic X-rays for tuberculosis or who were exposed to a large amount of radiation before age 30 -- usually as treatment for cancers such as lymphoma.
• Other cancer in the family. A family history of cancer of the ovaries, cervix, uterus, or colon increases your risk.
• Heritage. Female descendents of Eastern and Central European Jews (Ashkenazi) are at increased risk.
• Alcohol. Use of alcohol is linked to increased risk of developing breast cancer. Compared with nondrinkers, women who consume one alcoholic drink a day have a very small increase in risk, and those who have 2 to 5 drinks daily, have about 1.5 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.
• Race. Caucasian women are at a slightly higher risk of developing breast cancer than are African-American, Asian, Hispanic, and Native American women. The exception to this is African-American women are more likely to have breast cancer than causasians under the age of 40.
• Hormone Replacement Therapy (HRT). Long-term use of combined estrogen and progesterone increases the risk of breast cancer. This risk seems to return to that of the general population after discontinuing them for five years or more.