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Cancer Services
With the identification of the BRCA1 and BRCA2, genetic testing became a
possibility. It is important for women to understand the complexity of genetic testing. The
following provides information on the benefits and pitfalls of genetic testing as well as the
process involved.
In the following family, assume that the mother has a mutation in
one of her BRCA1 genes. The mother has two chromosome 17's, one with a normal BRCA1 gene, and one
with a BRCA1 gene that is mutated. The father has two chromosome 17's, each with a normal BRCA1
gene.
Both daughters were assumed to be at high risk. From testing, one
learns that her risk is extremely high, while the other learns that she has no increased risk at
all.
The availability of genetic testing will allow us to better define who is at the highest risk
of developing breast and ovarian cancer.
Benefits of Genetic Testing for Breast Cancer?
The value of genetic testing is very much dependent on a women's individual preference.
Genetic testing may:
What Are the Pitfalls of
Testing?
In order for someone at risk to be tested, an affected family member must first be tested. If an
affected relative (one with breast or ovarian cancer) is tested, and the family's specific mutation
is identified, the person at risk can then be tested. If the woman at risk is negative for the
family specific mutation, she is not at the high risk of her family. She must realize, however, that
her risk is not 0%. She has the same risk as the average woman, which is about 11%.
If she is found to have a mutation, there is no certainty when or if cancer will occur.
Though it has not been a common problem to date, there is concern that this woman may incur
insurance discrimination. Women who test positive for BRCA1 or BRCA2 mutations may have
trouble obtaining or keeping life insurance, health insurance, or disability insurance. Several
states have enacted laws with the hope of preventing this and there is some current and proposed
protective federal legislation.
Genetic information can have many emotional consequences for the person being tested. Individuals may feel
anxiety and/or depression as they await their result, and may experience many different emotions once they
receive their result. In addition, this information can have widespread implications for other
family members, and it may be difficult to inform relatives if an alteration is identified.
What Are the Processes Involved in Genetic Testing?
Genetic testing is an extremely complex laboratory process. The BRCA1 and BRCA2 genes are very
large, and mutations may occur at any location along the genes's length. The circles and dots
represent places in the BRCA1 gene where mutations have been found. Therefore, to determine if a
mutation exits, the entire BRCA1 or BRCA2 genes must be examined (sequenced) from end to end.
Genetic Testing Is a Family Matter
With the current technology, genetic testing of a living relative who has had cancer must be
done first in order to identify the family's specific mutation (A family carries only one mutation
in the BRCA1 or the BRCA2 gene). If we can identify the family mutation, we can then test an
individual who is not affected.
If no mutation is found in an affected person, it could mean one of two things.
2. A false negative, meaning that the family cancers are hereditary but are caused by a mutation
in another gene; or that the family mutation is in a location of BRCA1 or BRCA2 which can't be
tested. In these situations, a negative test would not be conclusive.
Prior to Testing
Before a person undergoes genetic testing, and the following should be considered:
If
we were to test the mother and determine that indeed she did have a BRCA1 mutation, we would then be
able to test the daughters for that same mutation (the family specific mutation). The daughter on
the left is found to have inherited 2 normal chromosomes, both with the normal BRCA1 gene and her
breast cancer risk is the same 11% as that of the average woman. The daughter on the right, however,
did inherit the mutated BRCA1 gene, and her risk for breast cancer is now up to 87% with a high risk of
ovarian cancer.
Each
daughter is assumed to have a 50% risk of developing breast cancer (and a high risk of ovarian
cancer). In actuality, each daughter does not have a 50% risk of developing breast cancer, but a 50%
risk of inheriting a mutated BRCA1 gene from her mother. She inherits only one of her mother's
chromosome 17's, either the one with the normal BRCA1 gene or the one with the mutated BRCA1 gene.
Her chance of getting the mutated BRCA1 gene is 50%. In the absence of a genetic test this is the
most we could tell the daughter.
Relieve uncertainty about chances for developing
cancer. For some, the possibility of bad news is preferable to uncertainty.
Explain cancers in the family
Assist in management decisions. Results of testing can
help with decisions about when to begin screening or whether to consider preventive surgery. 1. A true negative, meaning that the cancers are not hereditary.
Have family history
reviewed to determine if the family cancers are likely to be hereditary.
Have an understanding of cancer genetics and the meaning of a
positive or negative result.
Be psychologically prepared to receive the results and have a
management plan in mind.
Have a plan for who will know the results of the test and whether
insurance will pay for testing.
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