Q and A: Family medical history and your cancer risk

Reducing your risk of cancer means working on what you eat, what you drink, how often you exercise and other habits like smoking. But there are other risk factors that you can’t so easily identify.

Around 5-10% of cancers are caused by hereditary genetic mutations: Errors in your DNA passed down through your relatives. Having more than one relative with cancer can be a clue that a genetic mutation exists.

With 1 in 3 people diagnosed with cancer during their lifetime, it’s likely you have at least one family member who has faced this challenge. If you are a cancer survivor, you may be wondering if your children will inherit your disease. So when does a family medical history of cancer raise a red flag?

We talked to our genetic counseling team in the department of Clinical Cancer Genetics to find out more about the role of family history in your personal cancer risk.

How likely is it that a cancer is hereditary?

Only 5-10% of cancers are hereditary. It’s not uncommon for a mother and daughter or two sisters to have breast cancer and it not be linked to a hereditary cause. The rest is caused by lifestyle choices, by chance or by other unknown factors. If you are concerned about your risk for hereditary cancer, talk to your doctor or a genetic counselor.

Why is it important to know your family medical history?

In the case of cancer, family medical history matters because it can help us understand if we should be looking for a hereditary cause. Hereditary cancers are cancers that are caused by genetic mutations that can be passed down to other members of the family. Finding out a cancer is linked to a gene mutation may also open up more treatment options for someone who has already been diagnosed. These options should be discussed with a patient’s physician.

What should I look for in my family medical history?

Genetic counselors look for multiple family members with the same type of cancer. For example, two women with ovarian cancer, or two men with prostate cancer. They record what age those people were diagnosed. If a family member was diagnosed at an earlier than average age, it’s more likely their cancer was hereditary, and that may affect your risk of inheriting that cancer. It’s best to talk it all through with a genetic counselor who is trained in collecting family medical history. You can help by gathering details from your first-, second- and third-degree relatives. Ask them what illnesses they’ve had and at what age.

Your first-degree relatives are your parents, siblings and children. Your second-degree relatives are your aunts, uncles, nephews, nieces and grandparents. Your third degree relatives are your cousins and your great grandparents.

Why is it important to know if a cancer is hereditary?

It answers the question: Why did this cancer happen? If we know why it happened, that helps us in two ways. For the individual who has cancer, it may guide treatment options and lets us know if the patient is at increased risk for a different cancer in the future. Second, knowing a cancer is hereditary tells us other relatives may be at increased risk and may also benefit from seeing a genetic counselor.

If someone has hereditary cancer, what kind of treatment options are available?

There is constant progress in personalized cancer care. If we know the gene mutations that caused a cancer, we may be able to guide treatment based on the specific gene mutation. In the case of ovarian cancer, there are specific drugs for women with an underlying BRCA1 or BRCA2 mutation. If we know where the problem is in the genetic pathway, we can take advantage of that and attack the cancer. We look for the weaknesses of that cancer and take advantage of them.

How should people go about gathering their family medical history?

The first thing is asking family members what type of cancer they, or another relative had and at what age. For example, we know female cancers get confused all the time. We might hear a 15-year-old or 20-year-old in the family had ovarian cancer, but it’s more likely that was cervical cancer. That can make a big difference in terms of whether we’re worried about something hereditary or not. The best way to get the facts is talking to the family members who were affected. Whenever possible, get the death certificates on relatives who have died. This can help confirm cancer histories.