Q. Several female relatives on my dad's side of the family had breast cancer, and one has ovarian cancer. Does that mean I may be at higher risk for breast cancer, even though no one on my mom's side had cancer?

A. It is possible that you may be at increased risk for breast or ovarian cancer given the multiple affected family members on your father's side. The incidence of these cancers on either your mother's or father's side is equally important when assessing inherited cancer risk.

Here is why. The increased risk for breast and ovarian cancer in families with several diagnosed individuals is often due to a mutation in either of the breast cancer tumor suppressor genes, BRCA1 and BRCA2. Proteins produced by these genes contribute to DNA repair and help prevent cells from growing uncontrollably. Mutated BRCA genes may create malfunctioning proteins, resulting in an increased risk for cancer.


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Every individual inherits two copies of each gene, one from dad and one from mom. A strong family history of breast or ovarian cancer on the father's side — for example several occurrences among paternal grandparents, aunts, or uncles — raises the possibility that dad may have a BRCA mutation. If either parent has a mutation, each child has a 50 percent chance of inheriting it.

It is important to note that abnormalities in other genes have also been associated with increased breast and ovarian cancer risk. BRCA1 and BRCA2 are the most well known.

According to the National Cancer Institute only about 5-10 percent of breast cancers and 15 percent of ovarian cancers are due to known inherited BRCA mutations. However, these genetic mutations substantially increase the lifetime risk for these cancers, and are associated with cancers developing at a younger age.

If you have multiple occurrences of cancer on either side of the family, it may be useful to consult a genetic counselor who can determine if the pattern of cancer suggests you may be at increased risk and might benefit from genetic testing. There are guidelines regarding who should consider genetic testing available on the National Cancer Institute website. An online tool at knowbrca.org can also be helpful in evaluating family history.

Genetic testing is a personal decision with possible ramifications for the entire family. Knowing you have inherited a predisposition for cancer can allow you to make informed decisions about cancer risk reduction and increased surveillance. Your health care professional can provide guidance for your particular situation.

Teddie Keller volunteers with the Grillo Center, which offers free, confidential research to assist in health understanding and decisions. To use this service, contact us at grillocenterhealth.org, 720-854-7293 or 4715 Arapahoe Ave., Boulder. No research or assistance should be interpreted as medical advice. We encourage informed consultation with your health care provider.