Breast Cancer Risk Factors

Overview

Studies have shown that risk for breast cancer is due to a combination of factors. The main factors that influence risk include being a woman and getting older. Most breast cancers are found in women who are 50 years old or older.

Some women will get breast cancer even without any other risk factors that they know of. Having a risk factor does not mean you will get the disease, and not all risk factors have the same effect. Most women have some risk factors, but most women do not get breast cancer. Talk with your doctor about ways you can lower your risk and about screening for breast cancer.

Risk factors you cannot change

• Getting older. The risk for breast cancer increases with age. Most breast cancers are diagnosed after age 50.
• Genetic mutations. Inherited changes (mutations) to certain genes, such as BRCA1 and BRCA2, increase risk of breast and ovarian cancer.
• Reproductive history. Starting menstrual periods before age 12 and starting menopause after age 55 expose women to hormones longer, raising their risk of getting breast cancer.
• Having dense breasts. Dense breasts can sometimes make it hard to see tumors on a mammogram. Women with dense breasts are also more likely to get breast cancer.
• Personal history of breast cancer or certain noncancerous breast diseases. Women who have had breast cancer are more likely to get breast cancer a second time. Some noncancerous breast diseases such as atypical ductal hyperplasia or lobular carcinoma in situ are associated with a higher risk of getting breast cancer.
• Family history of breast or ovarian cancer. Having a family history of breast cancer may increase risk for breast cancer. For example, risk may be higher if a person's mother, sister, or daughter (first-degree relative) or several family members on either parent's side of the family have had breast cancer, or if a relative had breast cancer at a young age. A family history of ovarian cancer or breast cancer in a male relative also raises risk.
• Previous treatment using radiation therapy. Women who had radiation therapy to the chest or breasts (for instance, treatment of Hodgkin's lymphoma) before age 30 have a higher risk of getting breast cancer later in life.
  
• Exposure to the drug diethylstilbestrol (DES). DES was given to some pregnant women in the United States between 1940 and 1971 to prevent miscarriage. Women who took DES have a higher risk of getting breast cancer. Women whose mothers took DES while pregnant with them also may have a higher risk of getting breast cancer.

Risk factors you can change

• Not being physically active. Women who are not physically active have a higher risk of getting breast cancer.
• Being overweight or having obesity after menopause. Older women who are overweight or have obesity have a higher risk of getting breast cancer than those at a healthy weight.
• Taking hormones. Some forms of hormone replacement therapy (those that include both estrogen and progesterone) taken during menopause can raise risk for breast cancer when taken for more than 5 years. Certain oral contraceptives (birth control pills) also have been found to raise breast cancer risk.
• Reproductive history. Having the first pregnancy after age 30, not breastfeeding, and never having a full-term pregnancy can raise breast cancer risk.
• Drinking alcohol. Studies show that a woman's risk for breast cancer increases with the more alcohol she drinks.

Research suggests that other factors such as smoking, being exposed to chemicals that can cause cancer, and changes in other hormones due to night shift working also may increase breast cancer risk.

What Would You Tell Your Patients About Drinking Alcohol and Breast Cancer Risk?

CDC's Dr. Lisa Richardson explains the link between drinking alcoholic beverages and breast cancer risk in this video.

Who is at high risk for breast cancer?

If you have a strong family history of breast cancer or inherited changes in your BRCA1 and BRCA2 genes, you may have a high risk of getting breast cancer. You may also have a high risk for ovarian cancer.

Talk to your doctor about ways to reduce your risk, such as medicines that block or decrease estrogen in your body, or surgery.