Hereditary
Breast Cancer
Here we aim to give you information on breast cancer that runs in a family.
This is called hereditary breast cancer. It describes what hereditary
breast cancer is, how it is passed on, and the importance of family
history in guiding the search for changes in genes that can lead
to cancer.
Even though
this is mainly aimed at women, it may also be relevant to men
How common is breast cancer ?
Breast cancer is now the second most common cancer in Ireland. It affects over
2,000 women in Ireland every year. It is rare in women under the
age of 30 and occurs more often in women over the age of 50.
Men also develop breast cancer but this is very rare and about 15 men develop breast cancer each year in Ireland.
Top
What causes breast cancer ?
The cause of
breast cancer is still not fully known. A woman has a 1 in 12 lifetime
chance of developing breast cancer but some women are at a higher
risk of developing the disease. Experts believe that between 5-10%
of breast cancer cases are caused by changes that have been passed
on in certain key genes.
Top
What are the risk factors for breast cancer ?
There are some factors that increase a woman’s risk of developing breast
cancer over which we have no control.These include:
- Being
female
- Getting older
- Family history of breast or ovarian cancer
- Early Menarche (starting your period before the age of 12)
- Late Menopause (Change of life after the age of 55)
Other factors that can slightly increase our risk include;
- Being overweight
- Not being physically active
- Contraceptive pill
- Hormone Replacement Therapy (HRT)
- A history of benign breast disease
- First pregnancy after the age of 30
- Too much alcohol use
- Smoking tobacco
Top
What is hereditary breast cancer ?
Hereditary breast cancer occurs when a faulty gene is passed on from either parent. This greatly increases the likelihood that cancer will develop but
people can carry such genes and not develop breast cancer. It is
important to remember that hereditary breast cancer is rare.
Top
What are genes ?
Genes are a special set of instructions inside the cells of our
bodies that parents pass on to their children. Genes contain information,
telling our bodies how to work and grow. Genes are also responsible
for many things, like the colour of our eyes and the size of our
feet.
Top
How is breast cancer linked to Genes ?
Our bodies grow with a set of instructions delivered by our genes. Sometimes a gene develops a fault. As a result that cell may grow abnormally and
become cancerous. If you inherit a faulty gene at birth it means
that cells throughout the body are much more likely to develop changes
leading to cancer.
The instructions of each gene are like a code. Sometimes the code changes and is
different to a normal gene. For example, imagine the code for a
normal gene is:
1-2-3-4-5-6-7-8-9-10-11-12-13
A cancer gene passed down through a family may have a mistake, giving
a slightly different code:
1-2-3-4-5-6-7-8-9-9-10-11-12-13
This gene will give a different instruction to the cell it controls.
As a result, it can make it grow in a different way. Only when a serious change
occurs in the gene does a problem occur. There are a number of genes
that can cause breast cancer when they contain such faults.The two
most commonly tested for are called BRCA 1 and BRCA 2. Faults in
these genes are associated with high risks of developing breast
or ovarian cancer.
BRCA stands for BReast CAncer genes 1 and 2.
Top
Who might be at risk of having hereditary Breast Cancer ?
Those with:
- A blood relative who has developed cancer in both breasts
- Two or more first degree relatives with breast cancer under
the age of 50 or ovarian cancer at any age.
- A first degree relative with a known breast cancer gene.
- A male relative with breast cancer.
- An ethnic backround where a faulty gene is more commoly
inherited, for example, Ashkenazi Jews.
A first degree relative can be your mother or father, sister/brother or child.
Individuals
who inherit a known cancer gene will not definitely develop cancer,
but have a high risk of developing cancer compared to the wider
population.
Top
What should I do if I have a strong family history ?
If you are concerned about having a strong family history, it is important to discuss these concerns with your GP. You will be asked to give more information
on family members that have or have had breast, ovarian and other
cancers. Details will be required regarding the age at which the
family member first got cancer and the type of cancer(s) that developed.
You may then be referred to a family risk assessment unit.
Top
What happens at a family risk assessment unit?
At this unit your family history will be looked at more closely and, where possible, the information regarding cancer cases will be checked and confirmed.
Your personal risk of developing breast cancer will be defined,
if possible, as low, medium or high risk.
In some situations
it is very difficult to say if someone is a carrier of the breast
cancer gene. Genetic testing (screening) is not carried out at the
family risk assessment unit.
Top
What is genetic testing ?
Genetic testing involves taking a blood sample. This sample is sent to a specialist
laboratory to try and find the particular fault in the gene. Genetic
testing takes many weeks to carry out. The search for a fault is
like looking for a single spelling mistake in a very large book.
If you do require
genetic testing you will be given appropriate information and counselling
before the test takes place and after the result is available. Genetic
testing is currently only suitable for people with a strong family
history.
Top
Who can be tested ?
Genetic testing within a family consists of 2 stages:
- In order
to find the fault on the gene, a member of your family who has or
has previously had breast cancer has to be tested first.
- If a fault is found in that family member then genetic testing
can be offered to others in the family. It is an individual choice
for each family member whether or not they wish to be tested.
Genetic testing is carried out at the National Centre for Medical Genetics at Our
Lady’s Hospital at Crumlin and St. James Hospital Dublin.
Top
What kind of risk groups are there ?
Low risk:
This means your breast cancer risk is about the same as the
rest of the population. You should continue to be breast aware,
and attend the National Screening Programme when invited.
Medium risk: This means you have a medium risk compared to the rest of
the population. Depending on your age, you may be invited for a
mammogram and offered screening at a younger age and more regularly.
You will be given support and information that is relevant to your
needs.
High risk
This means you have a high risk of developing breast cancer
compared to the rest of the population. If you are at high risk
you need expert advice on how to reduce your risk and what measures
you need to consider in terms of screening, surgery, lifestyle and
medication
If you inherit a known breast cancer gene, it does not mean you will develop breast
cancer. Whatever your risk group, it is important to continue being
breast aware and to report any changes to your doctor. It is also
important to update your family doctor if any of your family develop
breast, ovarian or other cancers.
Top
Where can I get more advice ?
If you are concerned about a family history of breast cancer talk to your GP. He or she may refer you to a family risk assessment clinic. For further information
call the National Breast Cancer Helpline on 1800 30 90 40.
Top
|
