Breast Cancer (cont.)

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What causes breast cancer?

There are many risk factors that increase the chance of developing breast cancer. Although we know some of these risk factors, we don't know how these factors cause the development of a cancer cell.

What are breast cancer risk factors?

Some of the breast cancer risk factors can be modified (such as alcohol use) while others cannot be influenced (such as age). It is important to discuss these risks with your health care professional any time new therapies are started (for example, postmenopausal hormone therapy).

The following are risk factors for breast cancer:

  • Age: The chances of breast cancer increase as you get older.
  • Family history: The risk of breast cancer is higher among women who have relatives with the disease. Having a close relative with the disease (sister, mother, or daughter) doubles a woman's risk.
  • Personal history: Having been diagnosed with breast cancer in one breast increases the risk of cancer in the other breast or the chance of an additional cancer in the original breast.
  • Inherited genetic risks: Certain inherited genes, including BRCA-1 and BRCA-2, are associated with a significantly increased risk of breast and other cancers.
  • Women diagnosed with certain benign breast conditions have an increased risk of breast cancer. These include atypical hyperplasia, a condition in which there is abnormal proliferation of breast cells but no cancer has developed.
  • Menstruation: Women who started their menstrual cycle at a younger age (before 12) or went through menopause later (after 55) have a slightly increased risk.
  • Breast tissue: Women with dense breast tissue (as documented by mammogram) have a higher risk of breast cancer.
  • Race: White women have a higher risk of developing breast cancer, but African-American women tend to have more aggressive tumors when they do develop breast cancer.
  • Exposure to previous chest radiation therapy increases the risk of breast cancer.
  • Having no children or the first child after age 30 increases the risk of breast cancer.
  • Breastfeeding for 1 year or more over a woman's lifetime has been shown to lower the risk of breast cancer. Breastfeeding for a shorter time period may slightly lower the risk.
  • Being overweight or obese increases the risk of breast cancer.
  • Use of oral contraceptives in the last 10 years slightly increases the risk of breast cancer.
  • Using combined hormone therapy after menopause increases the risk of breast cancer.
  • Alcohol use increases the risk of breast cancer, and this seems to be proportional to the amount of alcohol used.
  • Exercise seems to slightly lower the risk of breast cancer in postmenopausal women.
Medically Reviewed by a Doctor on 9/25/2013

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