Genetic Testing and Breast Cancer
Who Should Undergo Genetic Testing for Breast Cancer?
Ms. G. is a 40-year-old woman with two small
children. Like most women, she is concerned about her chances of developing
breast cancer. She asks her doctor about her risks.
Although breast cancer is a worry for most women, Ms. G. is especially worried because of a
family history of breast cancer. Her mother and sister had breast cancers that were diagnosed
at young ages.
A woman with a family history of breast cancer
has a lot of concerns. Among other things, she is thinking of her job, children,
and husband, as well as how her medical insurance and health team will be able
to serve her needs in the future should a crisis arise.
What are the facts about families that have multiple members with breast cancer?
Overall, inherited breast cancer disorders account for a
small minority of breast cancers. Genes are the "messages" in
each cell of the body that determine the ultimate design of our bodies. Genes
can be damaged by the environment. Additionally, people can be born with defects
in the genes that remove the body's defenses against cancers. Only in about 10%
of all breast cancer cases is there actually a genetic defect that can be
tested. This means that 90% of breast cancers are due to other causes. In fact,
most cases of breast cancer occur in women who do not have a family history of
breast cancer. A complex interplay between environmental and genetic factors
affect the development of breast cancer, and all the key factors have not yet
Quick GuideBreast Cancer Diagnosis and Treatment
Breast Cancer and Genetic Testing Introduction
Intensive genetic counseling is required before undergoing genetic tests for
breast cancer. During this educational counseling session, the health care provider can fully explain the benefits and risks of genetic testing and answer any questions you may have.
You will also be required to sign a consent form prior to participating in any genetic tests. The form is an agreement between you and your doctor, showing that you have discussed the test and how its results might affect your family.
Here are some questions to consider when thinking about genetic testing:
- Am I prepared to cope with the result? Are my family members also prepared, including my children and my spouse?
- What are my goals for testing?
- How would I use my test results? What will I do differently if the results are positive, or if they are negative?
- Whom will I share my results with?
- Would a positive test result change relationships with my family?
What Happens During Genetic Testing?
Most importantly, you'll need to obtain a family pedigree to determine if there is a cancer development pattern within your family. A family pedigree is a chart that shows the genetic makeup of a person's ancestors, and is used to analyze inherited characteristics or diseases within a family.
After outlining the family pedigree, a blood test can be given to determine if you have a breast cancer gene. Keep in mind that the vast majority of breast cancer cases are not associated with a breast cancer gene. In addition, scientists do not know all of the genes that can cause breast cancer, so doctors can only test you for the known genes.
When someone with a cancer diagnosis and a family history of the disease has been tested and found to have an altered BRCA1 or BRCA2 gene, the family is said to have a "known mutation." If an association between the development of breast cancer and a breast cancer gene is made, then all family members willing to participate in genetic testing are asked to give a sample of blood. For many people, knowing their test results is important, because this information may help to guide future health care decisions for themselves and their families.
How Do I Interpret the Genetic Test Results?
A negative genetic test means that a breast cancer gene mutation was not identified. If genetic testing has previously identified a mutation in your family, then a negative test means you do not carry the specific mutation that was identified in your family. Therefore, you would have the same risk as the general population. If a BRCA1 or BRCA2 mutation has not been previously found in your family, a negative result should be interpreted cautiously.
In such cases, there is still a chance you are at an increased risk to develop breast cancer due to potential mutations in genes other than those we currently can test for.
A positive test result means that a mutation known to increase the risk of breast and ovarian cancer was identified. Knowing your cancer risk may help guide important health care decisions for you and your family.