What to know about genetic testing and personalized medicine


November 4, 2016

Your genes will play a growing role in your healthcare.


Personalized medicine is about tailoring treatment to individual patients based on their genetics.

Georgia L. Wiesner, M.D., director of the Vanderbilt-Ingram Cancer Center’s Clinical and Translational Hereditary Cancer Program, explains the “4 Ps” of personalized medicine, the benefits it offers.

Personalized medicine is:

  • Predictive: It can inform someone about their risks for certain health problems.
  • Preventive: By telling you what you’re at risk for, personalized medicine gives you the chance to take preventive steps, such a changing your diet or quitting smoking.
  • Personalized: Each person’s genes are unique.
  • Participatory: By giving people detailed information about their own health, personalized medicine encourages people to take action to safeguard it.

Here Wiesner answers common questions about how your DNA will influence your healthcare:

What are some examples of how personalized medicine is used?

Pharmacogenetics is the field of study involved with the way someone’s body reacts, or doesn’t, to medications. People can respond differently to the same medicine – statins, for example, commonly prescribed to help lower cholesterol – depending on their genes. The drugs work well for many people, but for others, they don’t help and instead create poor side effects. If a doctor knows a patient’s genetic makeup, he or she can avoid prescribing a drug that won’t help that patient.

Identifying gene mutations that cause cancer is another important application of personalized medicine. Some gene mutations are inherited; some are not. Certain cancers are influenced by genes and their mutations – for example, the BRCA gene mutation, related to some breast cancers, runs in families. Knowing whether there is a genetic component to someone’s cancer helps doctors pursue the right treatment.

Testing tumor DNA, Vanderbilt-Ingram Cancer Center uses personalized medicine this way. By looking at what genes are mutated or not in a tumor, doctors can better identify which anti-cancer drug is likely to work the best for a given patient. VICC uses this science to treat lung, colon and breast cancers and melanoma, among others.


What are the implications of genetic testing?

Doctors can use the results to decide what screening tests you should have, and the best way to monitor a disease if you’ve already been diagnosed. It can suggest the proper surgery. You may have an illness that can be treated with a targeted therapy (one that will work for people with certain genes). It can identify certain medications you should avoid.


Do I risk losing health insurance if a genetic test reveals I’m at high risk for something?

No. The Genetic Information Nondiscrimination Act of 2008 prevents health insurers and employers from discriminating against people based on their genetic information. (The law does not address other types of insurance, such as life insurance. )

Before this act, Wiesner said, her patients were hesitant to get genetic testing. Today, they worry more about whether health insurance will pay the cost of the test. Plans can vary on coverage, although most will pay for testing, she said. Check the details of your own plan. The cost for a test done at a doctor’s office is often much less. Depending on how many genes are tested, Wiesner said, the cost for genetic tests range about $450 to $1,000. Insurance may cover much or all of this.


How is genetic testing done?

Tests that use a blood sample are best, Wiesner said, but another common technique is analyzing the DNA found in a sample of saliva. The saliva is swiped from your mouth with a large swab or from an oral rinse. This method yields less DNA than the blood sample, and typically the person having the genetic test needs to avoid food and drink beforehand.


Can I afford genetic testing?

The cost to have individual genome scanning is dropping. Wiesner gave examples of the research costs for the entire genome to be analyzed from many thousands of dollars to about $1,000. However, the cost of interpreting and understanding the results is rising.

Interpretation is tricky, because your genome can reveal many genetic variations not involved with your health. Researchers are still decoding what’s significant to health and what isn’t. Furthermore, the relationship between certain genes and mutations is not clear-cut. It’s not a matter of a certain gene mutation directly causing a certain disease, Wiesner said. Recent research indicates that even genetically influenced diseases arise from the actions of many genes – and lifestyle and environmental factors – taken together.

For this reason, if you’ve obtained your genetic information – from, say, the online service 23andME or – you should take it to a genetic professional for interpretation. To find a genetic professional, check with the National Society of Genetic Counselors or American College of Genetics and Genomics for specialists in your area. Meeting with a genetic professional is much like going to to the doctor. Some insurance plans pay for this expense.

Usually, the genetic testing laboratory will check a person’s insurance coverage, Wiesner said, often after the test is sent to the lab. Patients can stop the test if they learn that it’s not covered by their insurance.


What are the limitations of genetic testing?

  • Not all gene mutations can be identified by a test, so the results are not comprehensive.
  • It’s unclear which mutations are relevant to health.
  • The results of the test indicate probability – your chances of having a certain condition. “Nobody can say ‘you have zero chance of having this disease,’ ” Wiesner said. Likewise, results don’t mean you’re surely doomed to a particular disease. Genes are influenced by many factors, such as your diet, where you live and more.