Genetic Testing: What You Need to Know

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What’s the future of genetic testing?

Without question, genetic testing will play a larger role in cancer risk assessment, detection, and treatment in the future.

The Human Genome Project and The Cancer Genome Atlas

The Human Genome Project was a huge undertaking in which government and private researchers mapped the entire sequence of human DNA (known as the human genome). The project took more than 10 years and was completed in 2003. Scientists now estimate that the 3 billion or so “letters” that make up the human genome contain about 25,000 genes. The next step is to identify these genes and learn what each one does. This basic genome map will allow researchers to identify cancer-related genes more quickly.

An even larger undertaking, The Cancer Genome Atlas (TCGA), is now under way. Researchers are working to map the genes of cancer cells to try to learn how those genes are changed to produce the cancer. The TCGA uses an integrated network of hundreds of researchers across the United States and Canada to collect tissue samples from people with certain types of cancer. This project will further our understanding of the genetic basis of cancer, making genetic testing more useful in the future.

Personalized treatment

There are some genetic tests – some available, and some still being developed – that may help a doctor choose a person’s medicines.

For example, some tests can show whether a person’s cancer is likely to respond to a certain treatment based on its gene changes. Many new cancer medicines are being developed based on the known gene changes often found in cancer cells. In some cases, doctors can now test cancer cells for these gene changes to find out if the treatment is likely to be helpful.

Other tests can show whether a person’s body can process certain medicines normally. Tamoxifen, for instance, is a drug that can be used to reduce the risk of breast cancer coming back. But the body must make a certain enzyme to activate the drug. Some studies suggest that tamoxifen may work better in women who inherited the genes that make more of the activating enzyme. Overall, though, studies have not yet clearly proven this link. They also have not shown that people who are tested have better treatment outcomes. Right now, most doctors give tamoxifen without genetic testing, but further studies may lead to different options in the future.

More is being learned all the time about the gene changes in cancer cells and about how people process drugs based on their genes. This is expected to give doctors useful information about choosing medicines in the future.

Better technology

At this time, genetic testing can cost a lot, and it can take several weeks to get the results. But as better technologies are developed, tests are becoming more accurate and are able to look at more than one gene at a time.

DNA chip technology is one example of this. These chips allow researchers to look for changes in many different genes at the same time and analyze which genes are active. In the future, this type of DNA testing may help doctors learn a person’s risk of developing different diseases. This could make it easier to customize treatment for that person.

Other areas of research may impact how important genetic testing will become. One is the field known as epigenetics, which looks at ways genes are turned on and off other than just through mutations. Another is the field of proteomics, which looks at patterns of proteins in the body. (Genes are the blueprints for making proteins.) Researchers in these fields are developing tests that may someday be used along with or instead of standard genetic tests.

Home-based genetic test kits

Over the past few years, some genetic tests, marketed for a number of purposes, have become available as at-home kits that can be bought on the Internet. The kits include a small container to collect a saliva sample or a swab to rub inside the cheek. A few require blood, so the consumer must visit a medical facility to have it taken. Users mail the sample to a lab, where it’s tested for genes related to cancer or other conditions.

These tests may give some people access to genetic testing who might not otherwise have it. But while many of the companies marketing these tests make some type of genetic counseling available, there are concerns about whether people will use it (especially before buying a test). The decision to have genetic testing is complicated, and without proper background information and counseling, people might not understand the full implications of getting tested. They also may not be able to interpret their test results correctly.

There are other concerns, too. According to the US Food and Drug Administration (FDA), which regulates the makers of genetic tests, some of these tests are not scientifically validated. Others give results that are only useful if the person has a full medical evaluation. The FDA notes that genetic tests are very complex and they should be done in a specialized laboratory. They further recommend that the results be interpreted by a doctor or genetic counselor who understands the value of the test and how to best interpret and use the results.

If you are thinking about using an at-home testing kit, talk to your doctor or a genetic counselor first. This will help you decide if such testing is right for you and help prepare you for what you might learn. You should know the pros, cons, and limits of genetic testing before you have it done. And most people will need a trained professional to help work out exactly what the results mean for them and their families.

Dealing with genetic information

Managing the information we get from genetic testing continues to be an important issue. Many questions about patient rights and privacy still need to be resolved, and may become even more complex in the future. Other gray areas include genetic testing of children up for adoption, testing children for diseases they might develop as adults, and prenatal testing. Both national and international legislation are needed to address these concerns.


Last Medical Review: 10/18/2013
Last Revised: 10/18/2013