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Being High Risk For Breast Cancer

A small number of Canadian women (approximately 1-2%) are at high risk for developing breast cancer in their lifetime. Generally, high risk refers to a woman, who over their lifetime has at least a 1 in 4 chance, or 25% risk, of developing breast cancer. In the case of rare geneticGenetic:
Related to or caused by the genes.
Any change in the DNA sequence of a cell. Mutations can be harmful, beneficial, or have no effect. Certain mutations may lead to cancer or other diseases.
in cancer influencing genesGene:
A segment of DNA that contains hereditary information.
, the risk of developing breast cancer can be as high as 85%.

What is high risk?

Although the definition of high risk can vary somewhat, the following list of criteria are generally included in most definitions of women who are at high risk of developing breast cancer. 

Women at high risk include those with one or a combination of the following risk factors:

Being assessed for your risk level

If you think you may be at high risk for developing breast cancer, the first step is to speak to a health care provider, who will do an initial assessment based on your family and medical history, and consider referring you to a genetic counsellor for further assessment – or to a high risk screening program or clinic. 

Some provinces have a high risk screening program, which will connect you with a genetics clinic for genetic counselling and possible testing, and provide regular breast cancer screening if you are confirmed to be high risk. If your province or territory does not have a high risk screening program, your health care provider can provide a referral for both a genetics clinic and for breast cancer screening if necessary.

Genetic counselling and testing

An estimated 5-10% of all breast cancer cases are thought to be hereditary or caused by known genetic factors. Genetic abnormalities, called mutations, in certain genes have been linked to an increased risk of developing breast cancer. A mutation in the BRCA1 or BRCA2 gene is one of the main known causes of hereditary breast cancer.

BRCA1 and BRCA2 are genes that help to protect us against breast and ovarianOvary:
A female reproductive organ in which ova or eggs are produced. The ovaries also produce the female hormones estrogen and progesterone.
cancer. They play an important role in helping to repair damaged DNADNA:
Short for Deoxyribonucleic acid. DNA is found in the cells of our bodies. It contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. Your DNA contains genetic information that is unique to you.
that could lead to uncontrolled cell growth. We all have these two genes; BRCA1 and a BRCA2.  However, when there is a mistake (or mutation) in the gene, DNA repair does not occur as it should. 

A person inherits one copy of these genes from each of their parents. This means a mutated BRCA gene can be passed down from either a person’s mother or father, or both. It also means that a man can inherit a mutated BRCA gene, increasing his risk for developing breast cancer. With every pregnancy, there is a 50% chance that the mutation can be passed to the child if the mother or father has a BRCA1 or BRCA2 mutation.

Women with a BRCA mutation have a much greater lifetime risk of developing breast cancer and are more likely to develop it at a younger age, usually before menopauseMenopause:
A natural part of a woman's aging process, when the ovaries start to make less estrogen and progesterone and the menstrual periods stop. This change typically occurs between the late 40s and mid-to-late 50s.
. Women with a BRCA1 or BRCA2 mutation have a 40-85% chance of developing breast cancer in their lifetime.

Women with a BRCA1 or BRCA2 mutation also have a high risk of developing ovarian cancer, compared to women who don’t have a BRCA mutation. Women with a BRCA1 mutation have a 25-65% chance of developing ovarian cancer, and women with a BRCA2 mutation have 15-20% chance of developing ovarian cancer in their lifetime.

Men with a BRCA mutation also have an increased risk of developing certain cancers.   Men with a BRCA2 mutation have a 5-10% risk of developing breast cancer in their lifetime, compared to a less than 0.1% risk in men without a BRCA mutation.

BRCA gene mutations are also associated with increased risk for developing some other cancers. In both men and women, a mutation in BRCA1 or BRCA2 increases the risk for pancreatic cancer, and a BRCA2 mutation can increase the risk for a type of skin cancer known as melanoma. In men, a BRCA2 gene mutation increases the risk for prostate cancer. For men with a known BRCA2 gene mutation, prostate cancer screening is recommended yearly starting between ages 40 and 45.

Genetic counselling is offered when individuals and/or families are thought to have a genetic risk of breast cancer. It is an important step to determine the level of breast cancer risk and options to consider for breast cancer screening, ongoing assessment, and risk reduction. 

Genetic counselling

Genetic counsellorsGenetic counsellor:
A health care provider with specialized training and experience in the areas of medical genetics and counselling.
are available to help you understand what your breast cancer risk is.  They can assess your breast cancer risk based on your personal and family medical histories. Several different computer software tools are used to assess a person’s breast cancer risk and whether they may be a carrier of a genetic mutation that increases the risk. If a genetic risk of breast cancer is suspected and you meet criteria for genetic testing, you will be offered genetic testing.

Deciding whether or not to have genetic testing is a a very personal choice. To help you make that decision, genetic counselling is an opportunity for you to discuss with a trained genetic counsellor the benefits and limitations of genetic testing and the implications of a positive or negative test result for you, your life decisions, your family members, and your health care options. 

Genetic testing

Generally a blood test (or sometimes a saliva test) is required to test for genetic mutations that predispose an individual to breast cancer. Most commonly in women and men with a strong family history of breast cancer, the test usually looks for mutations in the BRCA1 or BRCA2 genes. Sometimes testing for mutations in other genes that are known to increase breast cancer risk is also done.

If a person is eligible for genetic testing, they will be offered testing.  If a mutation is found, genetic testing can then be offered to other members of their family. A person’s siblings, parents, and children each have a 50% chance of having inherited the same genetic mutation.

It can take several months to get the test results. There are some situations where test results may be available sooner:

  • In certain ethnic groups, such as in people of Ashkenazi (eastern European) Jewish ancestry, where specific mutations have been identified and makes testing easier

  • When results are needed quickly for making medical decisions

  • If a mutation has already been identified in the family, testing is generally done for that specific mutation only

Why go for genetic testing?

Most people with a strong family history of breast cancer, and who have genetic testing, will not be found to have an inherited gene mutation. However, based on their family history these women and their relatives are often still considered to be high risk and are given similar recommendations for breast cancer screening and prevention as women with a known genetic mutation.

Screening & Monitoring

Women who are at high risk of developing breast cancer are advised to consider breast cancer screening at an earlier age than women at average risk. The age at which high risk women are recommended to start screening varies by province and territory, but may begin as early as age 25.  Breast cancer screening for women at high risk can occur through a provincial or territorial high risk screening program if one is available, or with a doctor’s referral to a screening clinic.

Screening for women at high risk of developing breast cancer may include an annual mammogramMammogram (also called mammography):
A low-dose X-ray of the breast. It is used to take images of the breasts and is an important screening tool for the earlier detection of breast cancer.
and MRIMagnetic Resonance Imaging (MRI):
An imaging technique that uses powerful magnetic fields and radiowaves to create detailed, 3-dimensional images of the organs and tissues in the body, such as the breast.
of the breast. An MRI is used in addition to a mammogram because younger, pre-menopausal women have greater breast densityDense breasts (breast density):
Dense breasts have less fat and more glandular and connective tissue. A woman’s breast density depends on her age and genetic factors. Breast density is a risk factor for breast cancer. Having “dense breasts” is a clinical diagnosis that can only be assessed by mammography.
, which can make it more difficult to see abnormalities with mammogram alone. Breast cancers in women who are at high risk tend to grow faster, and when available, the combination of MRI and mammogram is better at detecting breast cancer in this population than either technology alone.

Your health care provider will receive the results of your test and discuss any abnormal results with you. If you have an abnormal screening result, your doctor will refer you for more tests, such as additional imaging tests or a biopsy.

Preventive Treatment

If you are at high risk for developing breast cancer, you may be considering the steps you can take to reduce your breast cancer risk. There are a range of options available, some of which can significantly reduce your risk, including surgery and medication.  These options may have a significant impact on your life and can be difficult decisions to make, especially when you have not been diagnosed with breast cancer. You have time to consult with your health care provider and to make a decision about which option, if any, is best for you.

Risk-reducing surgery

A risk-reducing mastectomyMastectomy:
Surgery to remove all or part of the breast and sometimes other tissue.
(sometimes called a prophylactic or preventive mastectomy) involves surgery to remove one or both healthy breasts to reduce the risk of developing breast cancer. The procedure is similar to having a mastectomy to treat breast cancer, but axillaryAxilla (axillary):
Armpit or underarm area.
lymph nodesLymph nodes:
Small structures that filter lymph fluid for harmful substances. They contain immune cells that can help fight infection by attacking and destroying germs. Cancer can travel through the lymphatic system spread to the lymph nodes.
and chest wall muscles that lie under the breast tissue are not removed.

Risk-reducing mastectomy significantly reduces the chance that a person will develop breast cancer, but does not completely remove the risk. For women with a strong family history of breast cancer or who have a confirmed BRCA1 or BRCA2 mutation, a risk-reducing mastectomy that removes both breasts can reduce the relative risk of developing breast cancer by as much as 90-95%. This surgery offers the greatest protection against developing breast cancer compared to all of the other options that are currently available.

If you are at high risk and choose to have a risk-reducing mastectomy, you may have the option to have your breast(s) reconstructed. This can occur at the same time as the mastectomy, or you can choose to have breast reconstruction at a later date. A health care provider can help you to better understand your options.

Choosing to have a risk-reducing mastectomy is a big decision. You have time to consider what actions you want to take to reduce your breast cancer risk and weigh the benefits and limitations of each option. Some of the factors you may think about when considering whether to have a risk-reducing mastectomy are:

  • Your level of risk for developing breast cancer, which can be determined by your health care provider or genetic counsellor

  • Your plans to breastfeed any young children you may have. Having a mastectomy removes your breast tissue and means that you will be unable to produce breast milk or breast feed

  • Other options available to you for reducing your risk of breast cancer

  • How physical changes as a result of surgery may affect how you feel about your body image or sexuality

  • Your level of stress or concern about your risk for developing breast cancer and how it impacts your day-to-day life

Since women who carry a BRCA1 or BRCA2 gene mutation are also at high risk for developing ovarian cancer, a risk-reducing surgery called a prophylactic oophorectomy is recommended once a woman has completed her family, or after age 35, whichever is later. This surgery involves removing the ovaries and fallopian tubesFallopian tube:
The tube through which an egg travels from the ovary to the uterus. There are two fallopian tubes, one that connects each ovary to the uterus.
. In addition to reducing the risk of ovarian cancer, it also reduces a woman’s risk of breast cancer by about 50%. This surgery has been shown to reduce the risk of death by 77% in women with a BRCA1 or BRCA2 mutation.

If you are considering having a risk-reducing surgery, speak to a health care provider and ask for referral to a surgeon, who can discuss the benefits and limitations of these procedures with you.


Another option for women at high risk for developing breast cancer is to take medications that reduce breast cancer risk. When drugs are taken to reduce the risk for cancer in healthy individuals, this is known as chemoprevention. While chemoprevention can reduce the risk of developing breast cancer, it cannot completely remove it.

At this time, tamoxifen and raloxifene are the only drugs approved for use in breast cancer prevention in Canada.  These medications work by blocking the effects of estrogen on breast tissue and are taken once per day as a pill (by mouth).

Tamoxifen is a medication used in the treatment of breast cancer. For high risk women who have not been diagnosed with breast cancer, it can also be prescribed to reduce their breast cancer risk.  Tamoxifen has been shown to reduce the risk of breast cancer by about 50%.

Raloxifene (Evista) is a medication that is used in the prevention and treatment of osteoporosis. It is also prescribed to help prevent breast cancer in high-risk women who have gone through menopause and like tamoxifen is taken as a pill once per day. Raloxifene has been shown to reduce the risk of breast cancer by up to 40%.

Both tamoxifen and raloxifene have side effects related to their influence on estrogenEstrogen:
A female sex hormone that is produced mainly in the ovaries. A woman’s levels of estrogen fluctuate throughout her life. Estrogen has been linked to the development of breast cancer and may promote the growth of cancer cells.
in the body. Common side effects include hot flashes, vaginal dischargeDischarge (vaginal):
Fluid produced by glands in the vaginal wall and cervix that drain from the opening of the vagina.
and sometimes dryness. Both of these medications also have rare but serious side effects, such as an increased risk for blood clotsBlood clot:
A thickened mass of blood. Blood clots normally form to help stop bleeding (e.g. at the location of a cut), but when they form inside blood vessels they can cause serious health problems.
, though this risk is much lower with raloxifene. Tamoxifen also increases the risk for cancer of the uterus, although this risk is low. Premenopausal women taking tamoxifen must use a reliable method of birth control as it can cause birth defects. The benefits of reducing breast cancer risk should to be weighed against the risk of developing these rare side effects.

 You have time to learn about your options for reducing your breast cancer risk so that you can make an informed decision that is right for you. If you are a woman at high risk for developing breast cancer and are considering taking medication to reduce your breast cancer risk, speak to your health care provider who can discuss the benefits and limitations of chemoprevention with you.

Healthy lifestyle changes

Preventive surgery and chemoprevention currently have the most impact on reducing breast cancer risk for women who are at high risk. Whether you choose to take medication, have a risk-reducing mastectomy, or take no medical action at all, there are steps you can take in your everyday life to try to reduce your risk of breast cancer and other diseases, including:

  • having a healthier body weight

  • drinking less alcohol

  • keeping physically active

  • eating healthy

  • quitting smoking

However, it should be noted that the role of lifestyle changes in women at high-risk of developing breast cancer is unclear and further research is needed. 

Resources and support

If you find out that you are at high risk for breast cancer, you may experience a range of emotions: anxiety about the future, feeling overwhelmed by information and decisions you may have to make, or even relief that you know and can take steps to reduce your risk for developing breast cancer.

There are supports and resources available to help you learn more about what it means to at high risk for breast cancer. Your health care provider or genetic counsellor can direct you to reading material or resources in the community you may find helpful, such as support groups or online communities for people at high risk for breast cancer. Connecting with, asking questions, and learning about the experiences of others who are also at high risk for breast cancer can be helpful as you go through your own decision making process. 



Breastcancer.org. Prophylactic Mastectomy. Accessed January 31st, 2014.

Canadian Cancer Society. BRCA gene mutations. Accessed January 30, 2014.

National Cancer Institute. Surgery to Reduce the Risk of Breast Cancer. Accessed January 31, 2014

More Information:

About Breast Cancer