Your genetic counselor will help you figure out if your family history suggests an inherited pattern to the cases of breast cancer — and perhaps ovarian and other types of cancer — that have occurred. If so, an abnormal BRCA1, BRCA2, or PALB2 gene may be causing the cancer in your family. The only way to know for sure is to undergo genetic testing.
Genetic testing results are most meaningful when the process begins with a family member who has already been diagnosed with breast cancer or ovarian cancer. That may be you, or it may be your mother, aunt, sister, or another family member. Here’s why:
- Even if an abnormal gene linked to higher breast cancer risk is present in your family, not every person in the family will have inherited it. It’s more likely that someone who has had breast or ovarian cancer will have the mutation. Once you verify that a relative with cancer has an abnormal gene, then it’s very likely that the cancers in your family are being caused by this mutated gene. Family members who then test positive should consider themselves to be at high risk of developing breast, ovarian, and/or other cancers. Those who test negative can view their risk as similar to that of people in the general population.
- If a family member with breast or ovarian cancer tests negative for a known abnormal gene linked to breast cancer risk, then it’s possible that a strong pattern of cancer in your family is due to some other inherited gene yet to be discovered by researchers. Based on family history alone, you and your relatives still should consider your risk of breast and/or ovarian cancer to be higher than that of the general population.
Sometimes, there are no living relatives with cancer who can undergo genetic testing. A genetic counselor can help you decide who in the family is the best person to test and why.
Once a person has been found to have an abnormal BRCA1, BRCA2, or PALB2 gene, it makes the most sense to proceed by testing the relative most closely related to her (or him). If that next relative does not have it, she or he could not have passed it on to children. For example:
- If your mother's sister has an abnormal BRCA or PALB2 gene, the next person to be tested would be your mother. If her test is negative (no gene abnormality present), then you do not need to be tested, because she could not have passed the mutation on to you. If your mother's test is positive, you might then decide to be tested. If your mother is no longer living, then you might go ahead with testing on the basis of your aunt's test result.
- If you test positive for an abnormal gene, the next people to be tested would be your siblings and/or your adult children. If any of them test positive, then they could have passed the mutation on to their own children. If they test negative, then they could not have passed on the mutation.
These are just two possible scenarios. Your genetic counselor can help you determine what is right for you and your family’s situation.
Most experts advise against testing children under age 18 for abnormal BRCA and PALB2 genes because no safe, effective therapies currently exist to help prevent breast cancer in children so young. Furthermore, children are not yet old enough to decide for themselves whether they want information about their lifetime cancer risks. It is also possible that by the time today’s children reach adulthood, scientists will have discovered a new treatment to correct abnormal breast cancer genes before cancer has a chance to develop.