Breast Cancer on Dad's Side

Hi!!  Just wondering about BRCA testing, my dad has lost a sister, an aunt and a first cousin all under age 50 to Breast Cancer.  I'm encouraging my dad to have the BRCA testing...if it's negative does that mean my siblings and I are in the "clear"??  Or should we all be tested as well???    Any input on the BRCA testing would be great....thanks.  Jen

[Lisa Kessler, MS, CGC]

You have a significant family history of breast cancer on your father’s side of the family.  Your dad may benefit from talking with a genetic counselor who can take a detailed family history of all cancer diagnoses, and provide risk estimates for the chances that a BRCA 1 or BRCA 2 mutation is causing the breast cancer in your paternal family history.  A genetic counselor will also explain who in the family is most informative to test first.   In general, if possible, it is best for someone who has been diagnosed with breast and/or ovarian cancer to have BRCA1/2 testing first.   Having genetic counseling does not obligate people to have genetic testing.   Your father can find a genetic counselor through the National Society of Genetic counselors.  

As you know, BRCA 1 and BRCA 2 are two genes associated with an increased risk of hereditary breast and ovarian cancer.  The genes are inherited in an autosomal dominant way.  They can be passed equally to men and women.  Someone with a gene mutation in BRCA 1 or BRCA 2 has a 50% chance of passing it on to each child that they have, and a 50% chance of not passing it on.  

If your father is tested and he tests negative, then testing would not be indicated for you and your siblings.  However, unless there was a mutation previously found in one of your relatives with the cancer, we would not know why his test was negative.  Perhaps he was fortunate and did not inherit the mutation in the family or perhaps BRCA1 or BRCA2 are not the causes of the breast cancer in your family.  It is also possible that the testing did not detect a BRCA1/2 mutation that is present and is a false negative.  Because of this uncertainty, even if your father’s tests are negative, you would not be in the “clear”, but would remain at increased risk because of your family history.  If a mutation is found in the family, and you test negative for the family mutation, then this is known as a true negative, and your risk for breast cancer would be reduced back to the risk for the general population.