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Home Prevention Genetic Testing For Breast Cancer

Genetic Testing For Breast Cancer

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Breast cancers can run in the family, and genetic testing can be performed to tell you if you have inherited an abnormal gene that will increase their risk of developing breast cancer. Individuals will sometimes choose to have genetic testing so that they can take steps to decrease their risk of breast cancer. However, before getting tested, there are many factors that need to be considered. This article will give you an overview of genetic testing for breast cancer.

There are two types of mutations that can lead to the development of breast cancer, germ line mutations and acquired mutations. Germ line mutations are inherited, or passed from parent to children. Acquired mutations are not inherited, but instead develop along patient’s life. The mutations can be caused by exposure to environmental agents such as radiation, chemicals or viruses. These mutations may also develop without any obvious known cause. Most breast cancers are caused by acquired mutations where the cause for the mutation is not known.

What is genetic testing?

Certain genetic changes, called mutations in one or more genes passed down from your parents could lead to the development of cancer. Genetic testing is performed to detect changes in the genetic sequence that could potentially lead to the development of cancer. These genes include, but are not limited to, BRCA1 and BRCA2 (Breast Cancer Gene 1 and Breast Cancer Gene 2).

Mutations in BRCA1 and BRCA2, will increase the risk of developing breast cancer over a lifetime. About 5-10% of all breast cancers diagnosed are caused by inherited genetic mutations. Genetic testing uses blood or tissue samples to test for genetic mutations, particularly BRCA 1 and 2 that could lead to the development of breast cancer.

Who should consider genetic testing?:

Genetic testing is recommended only for women who have:

·         Two or more close family members affected with breast cancer, especially if diagnosed before menopause.

·         Multiple generations of close family (ie sisters, mothers, grandmothers and aunts) with breast cancer

·         Family members with more than one cancer, such as breast cancer involving both breasts or breast and ovarian cancer

·         Close family members who have tested positive with BRCA1 or BRCA2 mutation

What to ask yourself prior to getting tested?

·         Who should I meet with to discuss genetic testing, a genetic counselor, my family doctor or an oncologist?

·         Am I prepared and ready for the test result? Are my family members prepared?

·         What are my goals for the testing?

·         Whom will I share my results with?

What to ask your genetic counselor?

·         How would I use my test results?

·         What can I do if the results are positive, or if they are negative?

·         Costs and insurance coverage: Some health insurance companies may cover the costs. Your doctor might need to write a letter to explain why testing is necessary.

After testing

How to interpret the result

It is not always easy to interpret the result of genetic tests. The result may be:

·         Positive for a BRCA1 or BRCA2 mutation: This means that a mutation known to increase the risk of breast cancer has been identified.

o   Knowing your cancer risk may be helpful for medical and lifestyle decision for you and your family, and will also help to make a decision about prophylactic methods including surgery.

·         Negative: This means that BRCA mutations were NOT identified. Although mutation is not identified, if you have a family history of breast cancer you may still have an increased risk of developing breast cancer because there are mutations that cannot be identified by genetic testing.

o   If a mutation has been previously identified in the family member, then a negative test means you do not carry the specific mutation that that family member had.  

§  Your risk of developing breast cancer is not well known, you should continue to have regular screening as recommended by your doctor.

o   If a mutation has not been previously found in the family, a negative result needs to be interpreted carefully as you may have a mutation that is not covered by the test.

§  Your risk of breast cancer is still higher than the general population and you should follow your doctors recommendations regarding screening for breast cancer.

o   Positive for a genetic mutation with "unknown significance." This means that a genetic mutation has been identified, but it is not clear if the mutation increases the risk of breast cancer or not.

Genetic testing is done to assess the risk of developing breast cancer, it does not accurately predict who will or will not develop breast cancer.  Those with a family history of breast cancer may not have an abnormal gene, and not all women who have inherited one of these genes will develop cancer. Therefore, all recommended screening for breast cancer should be continued for those who are negative. Those with a positive test should consider the risks and the benefits carefully of treatments to decrease the risk of developing breast cancer.

For patients with positive BRCA mutation, lifelong risk of breast cancer is about 50-85%. This means that out of 100 women, 50-85 women with this mutation will develop breast cancer along their life. Therefore, if the test is positive, there is still a 15% to 20% chance of not developing breast cancer.

What can I do to reduce my risk of developing breast cancer if I tested positive for BRCA1 or 2?

•More frequent screening for breast cancer:

•Monthly breast self-examination starting at age 18.

•Breast exam done by doctors, twice a year beginning at age 25

•Mammogram annually, beginning at age 25 (or 10 years before the youngest breast cancer relative)

•Breast MRI annually, usually six months after the mammogram

Discuss with your doctor the potential benefits and risks of frequent screening.


Surgery such as mastectomy could be done to reduce the risk of developing cancer. This is called preventive surgery, and it can significantly decrease the risk of breast cancer by at least 90 percent. Talk to your doctor about the potential risks and benefits of preventive surgery.


Selective estrogen receptor modulator (SERM) such as tamoxifen or raloxifene can reduce the risk of breast cancer in women who have BRCA mutations. This is called chemoprevention.  Chemoprevention has possible side effects, talk with your doctor about your risks and potential benefits of these medicines.

For more information regarding medications to lower the risk of breast cancer please see the article entitled Medications to Reduce the Risk of Breast Cancer.

Genetic testing remains controversial and aside from the issues raised previously there may be other legal and psychological issues related to breast cancer genetic screening that were not addressed in the article.  You should discuss potential benefits and ramifications of the testing with your doctor or a genetic counselor prior to testing.



Hui Gao M.D. Ph.D., Harbin Medical University

Edited by Amber Seba, MD




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