BREAST CANCER RISK

What is breast cancer?

In 2012, breast cancer was the most frequently diagnosed cancer and the second most common cause of cancer deaths in Ontario women. The risk of breast cancer increases with age, peaking at age 70-74.

The risk of breast cancer increases with age, peaking at age 70-74.

Although relatively uncommon, breast cancer can occur in men as well. The My CancerIQ Breast Cancer Risk Assessment is based on studies involving only women so cannot give an accurate assessment of the risk of breast cancer in men.

The female breast is a complex structure that contains milk-producing glands (lobules), tubes to carry milk from the lobules to the nipple (ducts), blood vessels, vessels that carry lymph fluid to the lymph nodes (located under the arm, near the collarbone and in the chest behind the breastbone), and fatty tissue.

Most lumps in the breasts are benign, meaning they are not cancerous. Such lumps are caused by scar-like or fibrous tissues or are fluid-filled sacs or cysts.

If a tumour in the breast is malignant it means it has become cancerous. In cancer, the cells divide uncontrollably and can invade surrounding tissue. Cancerous cells can sometimes spread (metastasize) to other parts of the body.

Breast cancer can occur before a woman has stopped menstruating (pre-menopausal breast cancer) or after menopause (post-menopausal breast cancer). Although many of the risk factors for pre- and post-menopausal breast cancer are the same, there is growing evidence suggesting there are differences as well. For example, genetic and other medical factors may have a greater effect on the development of pre-menopausal breast cancer whereas lifestyle factors may play a greater role in post-menopausal breast cancer. More research is required to fully understand the differences between pre- and post-menopausal breast cancer.

Risk factors you can change or control

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  Alcohol consumption

  For breast cancer, there is no “safe limit” of alcohol consumption: even drinking small amounts of alcohol can increase your risk. Compared to no drinks a day, each daily alcoholic drink increases the risk of breast cancer by almost 10%. The ethanol in alcohol may damage the DNA of cells or allow other carcinogenic (cancer-causing) substances to more easily enter cells. In addition, there is evidence suggesting that alcohol increases the level of estrogen in the blood, which can stimulate the growth of some tumours.

  In addition to the direct effects of alcohol, women who are heavy consumers of alcohol may have a poor diet. Poor nutrition may contribute to the development of cancer. Supplements such as multivitamins with folate may help compensate for some deficiencies but is no substitute for a healthy diet and avoiding alcohol.
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  Adult weight gain

  Gaining body fat as an adult may increase the level of several hormones, including estrogen, and may stimulate cell growth. There is some evidence that taking hormone replacement therapy (HRT) may help to reduce the risk of post-menopausal breast cancer associated with adult weight gain. However, the best and healthiest way to reduce your risk is to achieve and maintain a healthy weight.
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  Physical activity

  Women who are physically active may have a reduced risk of breast cancer. Studies have shown that the most active women may have a 20% to 30% lower risk than inactive women. The exact reasons aren’t clear. Physical activity may protect against breast cancer by helping to regulate the levels of hormones and steroids circulating in the blood. It may also help people to achieve and maintain a healthy weight.
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  Prescription medications that contain female hormones

  • Oral contraceptives:

    Compared to women who have never taken oral contraceptives (birth control pills), those who do – or who have taken them in the past – may have a greater risk of breast cancer. When you stop taking oral contraceptives, the risk of breast cancer starts to decline. It’s important to talk with your doctor or nurse practitioner about both the risks and the benefits of oral contraceptives.

  • Hormone replacement therapy (HRT):

    Hormone replacement therapy (HRT) may be used to treat the symptoms of menopause such as hot flashes. Taking HRT, especially prolonged use of the combined form containing both estrogen and progesterone, may increase the risk of breast cancer. The risk quickly falls after HRT is stopped. If you are taking HRT, talk to your doctor or nurse practitioner about both the risks and the benefits of this medication.

Risk factors you can't change or control

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  History of benign breast disease

  Many women have non-cancerous (benign) breast conditions, which may appear as irregular lumps or cysts (fluid-filled sacs) in the breast. If your doctor has said you have benign breast disease it means it is not cancer. However some types of benign breast disease may increase your risk of developing breast cancer.
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  Genetics

  • Genetic mutations

    Every cell contains a genetic blueprint in the form of DNA. DNA tells the cell when to reproduce and what to do. A genetic mutation is a permanent change in the DNA of the cell. Some mutations occur by chance when cells reproduce or because of damage to the DNA. Other mutations are inherited from a parent (i.e., hereditary genetic mutations).

    Hereditary genetic mutations that increase a woman’s risk of breast cancer are rare, occurring in less than 1% of the population. When one occurs, however, it can significantly increase a woman’s risk of breast cancer. Probably the best-known mutations are in the BRCA genes (BRCA1 and BRCA2). Having a specific BRCA1 mutation means a woman’s lifetime risk of developing breast cancer is between 55% and 65%; for BRCA2 the risk may be between 45% and 49%. BRCA1 and BRCA2 mutations are also associated with an increased risk of ovarian cancer. Mutations in other genes (TP53, CHEK2, PTEN or CHD1) can also increase the risk of breast cancer.

    If you have a “blood” or first-degree relative (e.g., a parent, brother, sister or child) who has been tested and was told they have a known genetic mutation for breast or ovarian cancer, there is a possibility you may also carry the mutation. Talk with your doctor or nurse practitioner.

  • Family history

    Having first-degree “blood” relatives (mother, father, sister, brother or child) diagnosed with breast cancer – especially if the cancer was diagnosed at a young age – may double the risk of developing breast cancer. The more close relatives with breast and/or ovarian cancer, the higher the risk.

  • Ashkenazi Jewish heritage

    Women of Eastern European or German Jewish descent are more likely to have genetic mutations that can increase the risk of breast cancer. If you are of Ashkenazi Jewish descent, talk with your doctor about your risk of breast cancer.

• Reproductive history - menstruation, menopause, pregnancy and breastfeeding

  Hormones, especially estrogen, can encourage the growth of some types of breast cancers. Estrogen levels increase in woman when they go through puberty and start menstruating, change during pregnancy, and drop when breastfeeding (times when women do not menstruate) and after menopause (the cessation of menstruation). As a result, the lifetime exposure to estrogen is lower in women who:

  • start menstruating at a later age;
  • go through menopause at an earlier age.

  Different studies have used different ages to look at the relationship between age of menstruation and the risk of breast cancer. As well, there is some evidence that the typical age of menstruation may be changing in North America. As a rule, though, starting to menstruate at a younger age than most of your peers or going through menopause much later in life is associated with a greater relative risk of breast cancer. Less lifetime exposure to estrogen may help to keep down a woman’s risk of some types of breast cancer.

  When women are pregnant, changes occur in the cells of the breast to prepare for breastfeeding. These changes can make the cells more resistant to cancer later in life. The earlier in life a woman experiences these changes, the greater protection she has against breast cancer. As a result, women are at lower risk of breast cancer if they:

  • have children, particularly if they:
    • have their children at an earlier age or
    • have several children.
  • breastfeed, particularly for a cumulative total of a year or more.

• Chest radiation

  Radiation therapy is used to treat certain cancers, such as lymphoma, and in the past was used to treat diseases such as tuberculosis, postpartum mastitis, acne or an enlarged thymus gland. Women who received ionizing radiation therapy to the chest before age 30 and at least 8 years ago have a 4% to 6% increased risk of breast cancer. The risk is higher for women who were treated during puberty.
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  Prescription medications – tamoxifen and raloxifene

  Tamoxifen and raloxifene are prescription medications that block the effects of estrogen. They may be prescribed to treat breast cancer, to help prevent breast cancer in women at high risk, or to prevent bone-thinning (osteoporosis). Taking tamoxifen or raloxifene for five or more years may lower your risk of getting breast cancer. These medications have both risks and benefits so they are not appropriate for all women.

  Common brand names for tamoxifen include Nolvadex D®, Mylan-Tamoxifen®, Apo-Tamox®, Tamoxifene®, Teva-Tamoxifen®. Brand names for raloxifene include Evista®, Apo-Raloxifene®, Teva-Raloxifene®.

• Height

  Studies suggest that tall women may have a higher risk of breast cancer. The reasons aren’t clear but may reflect the influence of hormones and other factors that affect growth.

• Weight when you were born

  Women who were heavier than average at birth (usually defined as weighing more than 8.5 pounds) may tend to have a slightly higher risk of breast cancer before menopause. Why this occurs is not clear. It may reflect the effect of exposure before birth to higher levels of hormones circulating in the blood of the mother.

What you can do to protect yourself