Dear Dr. Donohue: I am concerned that my 33-year-old daughter will have breast cancer. I have no history in my family of breast cancer, but my husband’s grandmother, mother and sister all have had breast cancer with double mastectomies. I have heard that the DNA follows the mother’s side and not the father’s. Is this true or an old wives’ tale? Should she have a BRCA test? — D.C.
Answer: Most cases of breast cancer are sporadic, meaning there is no particular identifiable family risk to develop breast cancer. However, there are identified genetic risks, especially including the BRCA1 and BRCA2 genetic variants, which are worth testing for in certain situations.
The guidelines for testing a person for BRCA1/2 are complicated, and I don’t have enough space to even summarize them here. However, the family history you’ve given is probably not enough to recommend gene testing (unless there are other factors, such as an Ashkenazi Jewish background). The types of breast cancer (such as ‘triple negative” breast cancer) and the ages at which the family members were diagnosed are also important.
The genes for BRCA1/2 are autosomal, not X-linked, meaning that it doesn’t (much) matter whether they come from the maternal or paternal side. Slight differences due to something called epigenetic changes can mean people who inherit BRCA2 from their father tend to have their breast and ovarian cancers diagnosed at a younger age than if it came from their mother.
Ideally, the person who had the cancer (breast, ovarian, pancreas, and prostate cancers all are affected by BRCA genes) should get tested, not only for BRCA1/2, but other newly identified genetic susceptibility genes.
The best advice on whether testing for your daughter is appropriate would come from a genetic counselor.
