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Is cancer hereditary?

It can be. In fact, between 5% to 10% of cancers are hereditary.

¡®Hereditary¡¯ means the cancer risk can be passed down through a family member. This happens when a person is born with an inherited genetic mutation.

So, what are inherited genetic mutations?

Genes carry instructions that tell your cells what to do. Some of our genes carry instructions that help protect our bodies from developing cancer. A genetic mutation in one of these genes causes cells to grow and multiply rapidly. Not all genetic changes are harmful. But over time, some mutations can cause cancer to develop.

An inherited genetic mutation is one that can be passed down from a parent to a child. Scientists have identified hundreds of inherited genetic mutations that increase your risk for developing cancer.

For example, mutations in the BRCA1 and BRCA2 genes are linked to breast cancer, ovarian cancer and pancreatic cancer. Lynch syndrome increases your risk for developing several cancers, including colorectal and endometrial, and developing them earlier than normal. Lynch syndrome is caused by mutations in the MLH1, MSH2, MSH6, PMS2 and EPCAM genes.

How do you know if cancer is hereditary?

All cancers are genetic. When you look at the genetics of cancer, something has gone a little bit haywire with those cells in order for them to turn cancerous. The cells might have divided abnormally or grow where they¡¯re not supposed to grow. This is caused by genetic changes. Genetic changes in cancer can happen by chance, or they can be inherited.

To figure out if cancer is hereditary, we have to do genetic testing on healthy tissue, like blood or saliva. This is called germline genetic testing. This will tell us if the cancer was caused by an inherited genetic mutation.

Genetic testing is usually recommended for cancer patients diagnosed with:

• Breast cancer at age 50 or younger
• Colon cancer at age 50 or younger
• Ovarian cancer
• Pancreatic cancer
• Metastatic prostate cancer
• Other cancers, as recommended by your care team

You may also get genetic testing if you¡¯re a close relative of a cancer patient with a genetic mutation or if you have a family history of cancer.

How family history affects your cancer risk

In general, you may be at risk for an inherited cancer mutation if you have one or more first-degree relatives (parents, siblings, children) or second-degree relatives (nieces, nephews, aunts, uncles, grandparents) who were diagnosed with:

• Certain cancers before age 50
• The same type of cancer
• Two or more different cancers
• A rare cancer, such as male breast cancer
• A known cancer risk mutation, such as a BRCA1 or BRCA2 mutation

That¡¯s why it¡¯s important to map out your family history and discuss it with your doctor, so they can determine if you need genetic counseling or genetic testing. List your first- and second-degree blood relatives, any cancer diagnoses they had, as well as the age they were diagnosed and how the cancer was treated.  

There¡¯s a misconception that women can¡¯t inherit breast cancer risk from their father¡¯s side of the family. But that¡¯s not true. It¡¯s just as important for women to know the cancer history on their father¡¯s side of the family as it is to know about their mother¡¯s side of the family.

If a parent (male or female) has a BRCA1 or BRCA2 mutation, there¡¯s a 50% chance that each child of that parent will inherit that mutation, putting them at a greater risk for developing breast cancer and other cancers.

If you or a family member test positive for an inherited genetic mutation, your doctor may recommend more frequent cancer screenings, starting cancer screening earlier or making lifestyle changes. There may even be surgeries or medications available to help reduce the risk of cancer.

Is it hereditary if multiple family members have the same type of cancer?

Often, we see multiple people in a family with the same type of cancer but who do not have an inherited genetic mutation. This is not hereditary cancer. We call this familial cancer. In these cases, a family has more cases of a particular type of cancer than we expect. It could be due to lifestyle, environmental factors or genetic factors we can¡¯t test for yet. Even if no genetic mutation is found in a family, cancer screening recommendations can be made based on family history.

How can I lower my cancer risk?

Remember: just 5% to 10% of cancers are hereditary. So, most cancers are not caused by an inherited genetic mutation.

And while there¡¯s no way to completely prevent cancer, there are steps you can take to lower your risk for developing cancer.

• Eat healthy meals. Aim to fill at least two-thirds of your plate with vegetables, fruits, whole grains, nuts and seeds. Limit red meat and focus on lean protein like chicken, fish and beans. Avoid processed meats like bacon and deli meats.
• Stay active. Regular exercise supports your whole body, including your immune system. Aim for at least 150 minutes of moderate exercise or 75 minutes of vigorous each week.
• Maintain a healthy weight. A high body weight increases your risk for several types of cancer. Talk to your health care provider to find out what¡¯s a healthy weight for you.
• Limit alcohol. For cancer prevention, it¡¯s best not to drink alcohol. If you choose to drink, be aware of the risks, aim to drink less often and have fewer drinks.
• Don¡¯t smoke, vape or use any form of tobacco. There is no safe form of tobacco. The best way to quit is using medication and counseling. Access resources to help you.
• Get screened. Regular screening exams can find cancer at an early stage when the chances for successful treatment are highest.
• Get vaccinated. The HPV vaccine prevents six types of cancer and is recommended for everyone ages 9-26. If you are ages 27-45 and unvaccinated, check with your doctor about the benefits of the HPV vaccine. Children and adults should be vaccinated against hepatitis B.
• Practice skin safety. Protect your skin from harmful UV rays by seeking shade between 10 a.m. and 4 p.m., using sunscreen and lip balm that is SPF 30 or higher, wearing protective clothing and sunglasses, and avoiding tanning beds.

Catherine Skefos is a senior genetic counselor in the Clinical Cancer Genetics Program at MD Anderson. She provides cancer risk assessment and counseling to patients in the Endocrine Center.

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