Some of your relatives have had cancer. And, you’ve heard that people with a family history of the disease may be more likely to get cancer.

So, should you consider genetic testing to find out if cancer runs in your family?

Here’s what you need to know to make a more informed decision.

Most cancer cases aren’t related to family history.

Only about 5 to 10% of cancer cases are due to an inherited cause. Genetic testing is a powerful tool to identify those individuals who are at especially increased risk for developing certain cancers.

You can inherit abnormal genes from a parent. And, if you inherit one of these genes, you’re much more likely to develop cancer — and at a younger age.

Breast, colorectal, ovarian, prostate, pancreatic and endometrial cancers sometimes run in the family.

But most cancers are related to lifestyle choices like smoking, not exercising and eating unhealthy foods.

Map your family’s cancer history

You can begin to gauge your risk for an inherited cancer by mapping your family’s cancer history.

Start by using the Surgeon General’s Office Family Health Portrait or MD Anderson’s family history form. Then, speak with relatives to fill in as much information as possible.

Pay special attention to the cancer histories of first- and second-degree blood relatives. First-degree relatives include siblings, parents and children. Second-degree relatives include grandparents, aunts, uncles, nieces and nephews.

In general, people at risk for an inherited cancer have one or more first- or second-degree members who were diagnosed with:

• Cancer at a young age (before age 50)
• The same type of cancer
• Two or more different cancers in the same person
• A rare cancer, such as male breast cancer or sarcoma
• A BRCA1 or BRCA2 mutation

Discuss your family history with your doctor

Does your family history raise some red flags? Use your completed form to talk to your doctor about your cancer risks.

Based on your family history, your doctor may refer you to a genetic counselor, who will review your family medical history, discuss the role of genetics in cancer and perform a hereditary cancer risk assessment. This assessment covers:

• Your odds of having a genetic mutation
• An estimate of your cancer risks
• Personalized genetic testing recommendations
• Individualized cancer screening and prevention recommendations

Based on your cancer risk assessment, the genetic counselor may recommend genetic testing. This simply involves having blood drawn.

The best person to test is usually the person with cancer. After the mutation that caused the cancer is identified, we can test first-degree relatives — mother, sisters, daughters — to see if they also carry it.

Carefully weigh the pros and cons of testing

One of the benefits of knowing if you have a genetic mutation is that you can work with your doctor to monitor and address your cancer risks. This can help prevent cancer or find it early, when it’s most treatable.

But your decision won’t just affect you. It will also impact your family since your test results may forecast their cancer risks, too.

Some people worry that their results will make it harder for them to get insurance coverage. But group plans are prohibited by law from using genetic information to discriminate against you.

No matter what you decide, remember: finding out that you have a gene mutation doesn’t mean you’ll definitely get cancer. And, learning that you don’t have a gene mutation doesn’t guarantee that you won’t get cancer.

Karen Lu is a professor in the Department of Gynecologic Oncology and co-director for the Clinical Cancer Genetics Program at The University of Texas MD Anderson Cancer Center in Houston, Texas.

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