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BRCA1 and BRCA2 – Genetic testing for breast cancer and ovarian cancer

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Download the BRCA1 & BRCA2 Gene brochure

Individuals or families with a history of breast or ovarian cancer may want to consider BRCA1 and BRCA2 genetic testing to understand the risk of hereditary breast cancer and hereditary ovarian cancer, and help decide what risk reducing measures to consider.

What is hereditary breast cancer?

Cancer is unfortunately very common, with 1 in 2 people developing cancer at some point in their lifetime. Breast cancer occurs in 1 in 8 women; with 80% being diagnosed after age 50; while ovarian cancer occurs in about 1 in 75 women. Men can also develop breast cancer although this is rarer, accounting for only 1% of all breast cancer. Most breast cancer occurs by chance however about 5-10% is inherited. When breast cancer is inherited it may be caused by a mutation (fault) in one of the breast/ovarian cancer genes, known as BRCA1 and BRCA2, or in a different breast cancer associated gene. Currently we know that there are at least 10 genes which cause breast cancer.

Characteristics of Families with BRCA mutations

Several close relatives with breast cancer

Breast cancer diagnosed before the age of 45

"Triple negative" breast cancer

Bilateral breast cancer (cancer in both breasts)

Ovarian cancer

Increased frequencies of other cancers such as prostate and pancreatic cancer

Male breast cancer

Jewish ancestry

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What are genes?

We have approximately 25,000 genes in every cell of our body. Genes are our body’s instructions and determine how our body functions, develops and is maintained. Genes come in pairs and each gene has a code, which can be thought of as a long sentence with thousands of letters. Changes in this code can stop the gene working and are called mutations. Mutations in some genes, such as BRCA1 and BRCA2 can increase the risk of certain types of cancer because normally these genes prevent cancer by repairing mistakes in the cells.

How are BRCA mutations inherited?

Our genes come in pairs. This means that we inherit two copies of BRCA1; one from our mother and one from our father. The same is true for the BRCA2 gene. BRCA gene mutations can therefore be inherited from either parent. If a parent has a genetic mutation, there is a 50% chance that it will be passed on to each child.

Genetic testing for BRCA1 and BRCA2 Mutations: Genetic testing is performed on a saliva or blood sample and analyses the BRCA1 and BRCA2 genes to identify mutations which are likely to lead to an increased risk of developing cancer. There are three different tests available depending on an individual’s personal and family history:

Predictive testing: In families where the BRCA mutation has already been found it is possible to test for just the familial mutation.  If the mutation is not present then the relative is not at increased risk of cancer.

Ashkenazi Jewish mutation test: In Jewish families it is possible to test for 3 common mutations. These mutations are responsible for 97% of BRCA mutations in Jewish families.  Results will show the presence or absence of these 3 mutations.

Comprehensive BRCA sequencing: Comprehensive sequencing, examines the entire DNA code of the BRCA1 & BRCA2 genes in detail. It is preferable to test a living relative who has been diagnosed with breast or ovarian cancer first. When this is not possible an unaffected person can have genetic testing if they wish. Genetic testing usually takes 3-4 weeks, at which point a follow up consultation is scheduled. There are three possible outcomes of Comprehensive genetic testing:

A mutation is identified which is known to increase the risk of breast cancer and appropriate screening or treatment can be arranged. Predictive testing can be offered to appropriate relatives.

A genetic variation is found, but whether or not this is the definite cause of cancer is unknown.  Screening is based on the family history.

No mutation is identified. It is possible that there may be a different genetic mutation in the family and therefore breast screening may still be required, particularly when an unaffected person has been tested.

When a family has a history of only breast cancer and no BRCA1 and BRCA2 mutation is identified, there is usually no increased risk of ovarian cancer.

Cancer Risks Associated with a BRCA mutation

It is important to remember that not everyone who inherits a BRCA gene mutation will develop cancer and the estimated cancer risks associated with BRCA mutations vary. BRCA1 mutations are estimated to have up to an 85% risk of breast cancer and up to a 60% risk of ovarian cancer. Men with BRCA1 mutations have approximately a 20% risk of prostate cancer. Women with BRCA2 mutations have up to a 90% risk of breast cancer and up to a 30% risk of ovarian cancer. Men with BRCA2 mutations have a 5-10% lifetime risk of developing breast cancer, and approximately a 40% risk of prostate cancer. Individuals with BRCA2 mutations also have an increased risk of pancreatic cancer and possibly other cancers. Occasionally, a baby will inherit two BRCA2 mutations and will therefore have the congenital condition known as Fanconi Anaemia.

What if I am found to have a BRCA mutation

Women with BRCA gene mutations should have annual breast MRI from age 30 and annual mammograms from age 40. It is also important for all women to be ‘breast aware’ which means becoming familiar with how your breasts look and feel and noticing any changes unusual for you. Many women have lumpy breasts, which naturally change depending upon the time in your menstrual cycle and therefore it is best to check yourself at the same time each month (mid-cycle). If you notice a change in your breasts it is important to seek medical advice. Ovarian screening has not been shown to be beneficial and therefore some women may consider risk- reducing surgery.

Preventative medication: Two hormonal medications have been shown to lower the risk of developing breast cancer in BRCA2 carriers as well as women at increased risk, when taken for 5 years. These medications have some side effects and it is important to discuss these with a genetics expert or breast specialist, who should be able to discuss the benefits and side effects in detail.

Risk-reducing surgery: Some women who are found to have a BRCA mutation choose to have risk-reducing surgery to lower their risk of cancer. Surgery to remove the ovaries can be carried out from about 40 years of age, when women have completed their families, and when the risk of ovarian cancer starts to increase. Removing a woman’s ovaries before the menopause is also known to reduce the risk of breast cancer. If a woman decides to have her ovaries removed before the menopause she should consider taking hormone replacement therapy to help treat the symptoms. Risk-reducing surgery to remove healthy breast tissue (risk-reducing mastectomy) may also be considered by some women. This is a very individual decision and obviously needs careful consideration. If a woman wishes to consider this option, her breast surgeon can provide further information.  

Cancer Treatment: Certain chemotherapy treatments may also be tailored on the basis of a BRCA mutation. For example, platinum based chemotherapy and PARP inhibitors can be beneficial in treating cancer associated with BRCA mutations.

Men with BRCA mutations: Men with BRCA mutations should be breast aware and perform monthly self breast examination. Annual prostate screening with PSA tests should be arranged.

Our knowledge of cancer genetics is rapidly growing, and the information given summarises this to date. Please keep us informed of any significant changes in your family in the future as this may alter our advice to you. Please do not hesitate to contact us if you have any questions or concerns.

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Financial Issues

Some individuals may be concerned about difficulties with obtaining insurance coverage following genetic testing. Currently, there is a moratorium ensuring that individuals do not need to disclose predictive genetic test results. This moratorium is valid until 2019. 

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