Understanding Breast Cancer

by Health Canada

Breast cancer is one of the most common forms of cancer in women. While the causes of breast cancer are not fully understood, research shows that you can lower your risk of developing the disease or dying from it, by minimizing lifestyle and environmental risk factors and through breast cancer screening.

The number of breast cancer cases grew slowly from the 1960's to the early 1990's, but leveled off in 1993. One in nine women in Canada will develop breast cancer in her lifetime. In 2003, 21,100 Canadian women will develop the disease, and about 5,300 will die from it.

Risks of Developing Breast Cancer

Scientific researchers have identified some factors which increase a woman's risk of breast cancer. Having breast implants to change your breast size or shape, or to rebuild a breast after surgery, has not been found to be a risk factor for breast cancer.

Factors which have been consistently found to increase risk

• Being overweight/obese (only after menopause), based on your BMI
• Taking hormone replacement therapy
• Exposure of the breast to high levels of ionization radiation (i.e. x-rays) or lower levels before age 2, especially at a young age
• Having a first baby after age 30 or never having a baby
• Never breastfeeding
• Having a close relative(s) with breast cancer
• Gender: More than 99% of breast cancers occur in women
• Age: risk increases as you get older
• Early menstruation (before the age of 12)
• Late menopause (after age 55)

Factors which have been less consistently found to increase breast cancer risk

• Drinking alcohol
• Being physically inactive
• Smoking tobacco
• Using birth control pills. Note that although taking birth control pills appear to slightly increase a woman's risk of breast cancer, the risk of ovarian cancer is decreased.

Screening Mammography

If you are a woman between 50 and 69 years of age, you should have a screening mammogram( a breast cancer screening x-ray ) at least once every two years based on your personal risk factors and the advice of your health care provider.

In recent years, screening programs and better treatments have helped decrease the number of women who die from breast cancer. See your doctor about breast screening programs available in your province or territory.

Minimizing Your Risk

While there are risk factors for breast cancer that you cannot change (such as your age, your family history or your reproductive history), you can substantially reduce your risk by making positive changes to your lifestyle.

Lose excess weight. Even a small degree of excess weight, 5 kg. (11 lbs. and greater) is associated with increased breast cancer risk, especially among postmenopausal women.

Be physically active. Studies show that even moderate physical activity may reduce your risk by 30 to 40 per cent. Choose an exercise or activity that makes you feel warm and breathe harder (such as brisk walking) for at least 30 minutes on 5 or more days of the week.

Limit your intake of alcohol. Women who drink alcohol have a modestly increased risk. The more you drink, the greater your risk. Limit yourself to not more than one drink per day - 12 ounces (340 mL) of beer, 5 ounces (140 mL) of wine or 1.5 ounces (42 mL) of spirits.

Breastfeed your baby. Breastfeeding seems to offer some women protection against breast cancer and it's good for the baby. Breastfeed for at least four months.

Quit smoking. Smoking tobacco and breathing second-hand smoke have been linked in some studies to breast cancer. Tobacco smoke is responsible for 30 per cent of all cancer deaths.

Talk to your doctor about the risks and benefits of hormone replacement therapy (HRT). HRT can relieve symptoms of menopause and reduces the risk of osteoporosis and colon cancer. However, HRT increases the risk of breast cancer and heart disease.

Although there is no compelling evidence suggesting that exposure to pesticides and other potentially harmful chemicals is related to breast cancer risk, it would still be prudent to minimize exposure to these agents. Follow the warnings and handling procedures in material safety data sheets (MSDSs) that are available for most chemicals. Work with your employer to ensure that your workplace has good air quality and that chemicals are properly handled.

About the Author

www.hc-sc.gc.ca
Health Canada is the Federal department responsible for helping Canadians maintain and improve their health, while respecting individual choices and circumstances.