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Research studies have shown that the likelihood of developing breast cancer has been linked to certain risk factors.

People who develop breast cancer may or may not have some of these risk factors.

Having a risk factor does not mean you will develop breast cancer.

Not all risk factors have the same amount of risk.

We have control over some but not all risk factors.

Being A Woman 
1 in 9 women who live to the age of 85 years will develop breast cancer in their lifetime.
About 1% of breast cancer occurs in men

Growing Older
8 out of 10 breast cancers are diagnosed in women 50 and older

Personal History of Breast Cancer
If a person has had breast or ovarian cancer before, there is an increased risk of getting it again.  It can return in the same breast, the other breast or in another part of the body.  This is called a recurrence. 

Family History of Breast Cancer
Only 5 – 10 % of breast cancer is due to an inherited change in a gene (BRCA1 or BRCA2).
Some family histories suggest a genetic predisposition to breast and/or ovarian cancer. This history may include the following on either the mother or father’s side of the family.

• Breast cancer diagnosed before the age of 35
• Male breast cancer
• Breast and ovarian cancer in one person 
• Breast cancer in Ashkenazi Jewish families
• Breast cancer in 2 first or second degree relatives under the age of 50
• Breast cancer in 3 or more relatives on the same side of the family

If you are concerned about your family history, talk with your doctor, who can help decide if a referral to a genetic counselling clinic is appropriate for you.

Previous Abnormal Breast Biopsy
Some benign (non-cancerous) lumps are associated with breast cancer risk. If you have had a benign breast lump and have concerns about your risk for breast cancer, talk with your doctor.

Increased Breast Density on Mammogram
A woman with high breast density may have an increased risk of breast cancer, similar to that of a woman with a family history of breast cancer.

As women grow older, the level of the female hormone estrogen decreases and women’s breast tend to become less dense.

References: answers to your questions about breast density in mammograms –CCO 2007.

Women with dense breast tissue are considered to be at increased risk of developing breast cancer and should be screened regularly – the policy of the Ontario Breast Screening Program is to screen women with dense breast tissue every year, instead of every two years.

References: OBSP Key Messages Re: Breast Cancer Screening for Women with Dense Breasts, 2007

Early Menstruation/Late Menopause
Women who have their first menstruation (period) before age 12 and their menopause (not having a period for one year) after the age of 55 are more likely to develop breast cancer.  This is thought to result from the longer exposure to the body’s female reproductive hormones.

On Hormone Replacement Therapy (HRT) For More than 5 Years
Women are given HRT to reduce some of the symptoms of menopause, such as hot flashes, vaginal dryness, night sweats and insomnia and also to reduce the risk of osteoporosis (weakening of the bones).

HRT is also known to increase the risk for breast cancer if taken for more than 5 years.  It can also increase the risk for stroke.

Discuss with your doctor whether HRT is right for you for a shorter period of time.

Fewer Births or Later Age of First Birth
Women who have never been pregnant seem to be more at risk than women who have had a child before 35.

Not Having Breastfed
Women who breastfeed for a year or more have a lower risk for breast cancer.

Radiation Therapy to the Chest Wall
Radiation to the chest can increase the risk for breast cancer because it causes damage to the cells.  When the cells are damaged, there is an increased chance of developing cancer. Studies have shown that there is an increased risk for breast cancer following radiation therapy to the chest wall for the treatment of Hodgkin’s disease.

Body Weight
Women who are overweight have a higher risk for breast cancer.  Breast cancer is linked to high levels of estrogen.  After menopause, most of the body’s estrogen is produced in fat tissue, so a woman who has more fat tissue is exposed to more of the hormone estrogen. If a woman is exposed to more estrogen, her risk for breast cancer is increased.

Physical Activity
Studies have shown that being physically active lowers the risk for breast cancer for both premenopausal and postmenopausal women. Talk to your doctor if you are starting or changing your physical activity.

Alcohol Use
Studies have shown that drinking 1-2 drinks per day will increase the risk for breast cancer. It does not matter if it is liquor, wine, a cooler or beer. Alcohol causes an increase in estrogen, which causes an increase risk for breast cancer. For postmenopausal women, the estrogen increase is more pronounced.

Smoking
Studies have shown that women who begin smoking or who are exposed to second-hand smoke starting in adolescence have an increased risk for breast cancer. This is because in adolescence, the breasts are still developing and are more sensitive to cancer-causing agents such as tobacco smoke.

Making Healthy Lifestyle Choices

• Maintain a healthy body weight
• Follow a healthy diet (low fat/high fibre)
• Be physically active
• Minimize your alcohol consumption
• Quit smoking
• Consider the risks and benefits of hormone replacement therapy, especially for more than 5 years
• Recognize your hereditary risk

References  - Canadian Breast Cancer Foundation