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), has now begun. Researchers are proposing to map the genes of cancer cells to try to learn how those genes changed to produce the cancer.
The National Cancer Institute (NCI) and the National Human Genome Research Institute (NHGRI) evaluated a smaller version of the project. The TCGA pilot project was a success, and TCGA started another program to improve the ability to diagnose, treat, and prevent cancer. The goal of their planned 5-year program is to chart the gene changes involved in more than 20 types of 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. These projects 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. These tests can find out whether a person’s body can process certain medicines normally. Tamoxifen, for instance, is a drug that is used to reduce the risk of breast cancer coming back. But the body must activate the drug by using a certain enzyme. 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 shown that people who are tested have better treatment outcomes. Right now, most doctors give tamoxifen without genetic testing, but further studies may give patients different options in the future. More is being learned all the time 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. As better technologies are developed, tests will become more accurate and will be able to look at more than one gene at a time.
DNA chip technology is one exciting area of genetic research. These chips are able to pick out gene fragments for specific diseases. The p53 DNA chip is now being marketed as a way to detect this specific genetic mutation, which is often linked to cancer.
Laboratory researchers are now able to put DNA from cells in a DNA chip scanner 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 how genes are turned on and off. 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 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 is tested for genes related to cancer or other conditions.
These tests are marketed for a number of purposes. And they 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). Genetic testing is complex, and without proper background information and counseling, people might not understand the full implications of getting such testing. They also may not be able to interpret their test results.
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 so complex 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 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 limitations of genetic testing before you have it done. And most people need professional help in working 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.
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