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. 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.

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 early and starting menopause at an older age 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. Taking forms of hormone replacement therapy (HRT) that include both estrogen and progesterone during menopause can raise risk for breast cancer. The risk depends on the type of HRT and each woman’s individual situation. Some birth control pills can raise breast cancer risk. Talk to your doctor about how hormones could affect your 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.

Who is at high risk for breast cancer?

Some people may be at high risk of getting breast cancer, such as those with a strong family history of breast cancer or inherited changes in the BRCA1 and BRCA2 genes.

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

Breaking Down BRCA

This video explains the importance of BRCA genes in fighting cancer. Changes in these genes can raise a person’s risk for breast, ovarian, and other cancers. Learning about your family history of cancer can help you and your health care provider understand your cancer risk.