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Risk Factors for Breast Cancer

A risk factor is something that increases your chances of getting a disease or condition.

It is possible to develop breast cancer with or without the risk factors listed below. It is also important to note that breast cancer can and does occur in women with no known risk factors. Generally, the more risk factors you have the greater your likelihood of developing breast cancer. If you have a number of risk factors, ask your doctor what you can do to reduce your risk.

The most common risk factors, gender and age, cannot be changed. Breast cancer is found mainly in women though it can also develop in men. While breast cancer can be found at any age, the risk increases with age. The majority of women diagnosed with breast cancer are over 50 years old.

Other factors that may increase your chance of breast cancer include:

Family History

Only about 15% of women with breast cancer have a family history of breast cancer. The risk is determined by how close the relations are and how many family members have breast cancer. For example, one first-degree relative such as a parent, sibling, or child with breast cancer can double an individual's risk of breast cancer. If there are two first-degree relatives with breast cancer, then an individual's risk is 3 times higher than average. Having one second-degree relatives such as aunts, nieces, or grandparents with breast cancer does not increase an individual's risk of breast cancer. However, having two second degree relatives with breast cancer does increase risk.

Having male relatives with breast cancer also increases the risk of developing breast cancer, but the risk levels are not as clear.

Genetics

Families with a high risk of breast cancer may consider genetic testing to determine if known genetic factors are causing the increased risk. Genetic mutations are changes in specific cell DNA that allow cancer to develop. These mutations are inherited from the parent instead of developing over time. The 2 most common genetic mutations occur in BRCA1 and BRCA2 genes. They are linked to the largest increase in lifetime risk. Women with the BRCA1 or BRCA 2 genes are at a higher risk for:

  • Breast cancer at an earlier age
  • Breast cancer in both breasts
  • Ovarian cancer

There are a number of other genetic mutations that are associated with breast cancer, but BRCA genes are by far the most common cause of family-related breast cancer.

Medical Conditions

Current or a history of certain medical conditions have been found to increase the risk of breast cancer. These may include:

  • Breast cancer or other abnormalities of the breast tissue
  • Breasts that have a high proportion of lobular and ductal tissue instead of fatty tissue, which makes the breast tissue more dense
  • Previous breast exposure to radiation therapy before age 30 years
  • Pregnancy after age 30 years, or no pregnancy at all
  • Absence of breastfeeding
  • Excess weight, particularly after menopause
  • Increased exposure to estrogen, which includes:
    • First menstrual period before age 13 years
    • Menopause after age 51 years
    • Prolonged use of hormone replacement therapy particularly after menopause
  • Previous biopsy results that indicate the appearance of abnormal cells, lobular carcinoma in situ, or radial scar formation. Tissue that is biopsied is examined under a microscope.

Lifestyle Factors

Lifestyle factors that increase breast cancer risk include:

  • Consuming 3 or more alcoholic drinks per day
  • A sedentary lifestyle
  • Smoking
  • Consuming a diet that is high in red meat
  • Use of oral or injected contraceptives

Ethnicity

In the US, Caucasian, Hawaiian, and African American women have the highest rates of breast cancer. The lowest rates occur among Korean, American Indian, and Vietnamese women.

Revision Information

  • Breast cancer risk factors. American Cancer Society website. Available at: http://www.cancer.org/cancer/breastcancer/detailedguide/breast-cancer-risk-factors. Updated January 15, 2016. Accessed February 11, 2016.

  • Breast cancer. Merck Manual Professional Version website. Available at: http://www.merckmanuals.com/professional/gynecology-and-obstetrics/breast-disorders/breast-cancer. Updated September 2013. Accessed October 21, 2015.

  • Breast and ovarian cancer and family history risk categories. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/genomics/resources/diseases/breast%5Fovarian%5Fcancer/risk%5Fcategories.htm. Updated June 17, 2014. Accessed February 11, 2016.

  • General information about breast cancer. National Cancer Institute website. Available at: http://www.cancer.gov/types/breast/patient/breast-treatment-pdq. Updated August 13, 2015. Accessed October 21, 2015.

  • Risk factors for breast cancer. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated October 9, 2015. Accessed October 21, 2015.

  • 6/24/2014 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Farvid MS, Cho E, Chen WY, Eliassen AH, Willett WC. Dietary protein sources in early adulthoood and breast cancer incidence: prospective cohort study. BMJ. 2014;348:g3437.