Risk Factors

Causes of Breast Cancer

Most women who develop breast cancer have no risk factors other than simply being a woman and getting older (especially being over 50). Talk to your doctor about your risk.

Other risk factors for breast cancer include:

• having had breast cancer before
• family history of breast cancer (especially in a mother, sister or daughter diagnosed before menopause or if mutations on BRCA1 or BRCA2 genes are present)
• family history of ovarian cancer
• an above-average exposure to the hormone estrogen, which your body naturally produces, perhaps because you
  • have never given birth or gave birth for the first time after age 30
  • began menstruating at a young age
  • reached menopause later than average
  • have taken hormone replacement therapy (estrogen plus progestin) for more than five years
• dense breast tissue (as shown on a mammogram)
• a history of breast biopsies showing certain breast changes, such as an increased number of abnormal cells that are not cancerous (atypical hyperplasia)
• radiation treatment to the chest area (for example, to treat Hodgkin lymphoma), especially before age 30

Source: The Canadian Cancer Society at www.cancer.ca