Risk Factors




Gender:  Women are 100X's more likely to develop breast cancer than men.

Age: Your chance of getting breast cancer increases as a woman gets older.

Genetic risk factors*: About 5 - 10% of breast cancers are thought to be linked to inherited changes (mutations) in certain genes.

Family History: Breast cancer risk is higher among women whose closet blood relatives have this disease.

Personal history of breast cancer: A woman with cancer in one breast has a greater chance of getting a new cancer in the other breast or in another part of the same breast.

Race: White women are more likely to develop breast cancer than other ethnic groups.

Dense Breast Tissue: It is harder for doctors to detect a problem on the mammograms for a woman with dense breast tissue.

Certain benign breast problems

Menstrual periods: Early onset of menstrual period (before age 12).  Generally the more menstrual cycles you have over a lifetime, the higher your breast cancer risk. [3]

Women with lobular carcinoma in situ (LCIS): Studies show that a LCIS diagnosis increases your risk of developing breast cancer by 7 to 11 times.


Obesity and a high-fat diet: Various studies link obesity and a high fat diet with an increased risk of breast cancer and heart disease. 

Physical inactivity - Women exercising for five or more hours per week experienced greater decrease in risk of developing invasive breast cancer compared to less active women.

Alcohol: Women who have 2 to 5 drinks daily, have about 1.5 times the higher risk than women who drink no alcohol.  

Long-term, post-menopausal use of combined estrogen and progestin (HRT) - Studies have shown that daily use of combined HRT increases a woman's chance of developing breast cancer by about 5% to 6% with each year of use.

Oral contraceptives: Studies have found that women using birth control pills have a slightly greater risk of breast cancer than women who have never used them. This risk seems to decline back to normal over time once the pills are stopped (in 10 years).

Environmental risk factors: Exposure to pesticides, or other chemicals, is currently being examined as a possible risk factor.

Number of childbirths: The more children a woman has given birth to, the lower her risk of breast cancer.  After the first child, each childbirth lowers risk. Women with no children have a small increase in breast cancer risk compared to women who have had more than one child [1].   

Age at childbirth: Women who have had no children or who had their first child after age 30 have a slightly higher breast cancer risk. [2]  


An ounce of prevention is worth a pound of cure. Despite all of the medical advances in the treatment of breast cancer (and the advances to come in the treatment of triple negative breast cancer), the best survival strategy is to prevent the onset of the disease.  Most researchers and physicians acknowledge that there is no fool proof prevention plan for breast cancer.  But many clinicians agree that there are some lifestyle changes that you can make to reduce your risk of developing triple negative breast cancer (TNBC) and other forms of breast cancer.  

* Although you can not change your genes, having a strong family history of breast cancer on EITHER your mother or father's side may mean you are at an increased risk for breast cancer.  Speak to your doctor about whether or not you should see a genetic counselor to consider getting tested.  This information can help you and your doctors tailor your care to reduce your risk for developing cancer.

What is a risk factor?

A risk factor is anything that may increase a person's chance of developing a disease. It may be an activity, such as smoking, diet, family history, or many other things. Different diseases, including cancers, have different risk factors.  In 1940, the lifetime risk of a woman developing breast cancer was 5%, or 1 out of 20 women would develop breast cancer within their lifetime.  In 2009, the American Cancer Society estimated that risk to be 13%, or almost 1 out of 8 women expected to develop breast cancer in their lifetime. 

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.  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.  


[1] Willett WC, Tamimi RM Chapter 20: Nongenetic Factors in the Causation of Breast Cancer, in Harris JR, Lippman ME, Morrow M, Osborne CK. Diseases of the Breast, 4th edition, Lippincott Williams & Wilkins, 2010.

[2] The American Cancer Society  http://www.cancer.org/Cancer/BreastCancer/DetailedGuide/breast-cancer-risk-factors

[3] Breast Cancer Research  "Triple-negative breast cancers are increased in black women regardless of age or body mass index" 2009; 11: R18

Last Medical Review: August 2010