What Is Genomic Testing?: A HealthCentral Explainer
In the spring of 2003, scientists announced the completion of the Human Genome Project, a daunting undertaking in which they mapped the entire human genome. Already, this is having a profound effect on medical research and treatment and that will only increase in the coming years.
Here’s what you should know about this fast-growing field.
What is genomics?
First, it’s important to distinguish between two terms that are often used interchangeably, but in fact refer to two separate areas of research—“genetics” and “genomics.” Below are key differences between the two:
What is the purpose of genomic testing?
When scientists first sequenced the human genome, it took approximately $3 billion dollars and 15 years. Since then, technological advances have allowed researchers to sequence genomes at a much higher speed and lower cost. Now scientists are able to search for all genetic alterations in DNA that may affect the risk of developing cancer and other diseases.
Through genomics, researchers are able to test for and treat complex diseases that are caused by variations in more than one gene, such as diabetes and cardiovascular diseases. Researchers hope that they may one day be able to prevent such diseases by better understanding how genes interact with the environment, in addition to more clearly identifying non-genetic factors over which people have control, such as diet and exercise.
What progress has been made with genomic testing?
Since the Human Genome Project was completed, scientists have been able to compare genetic differences among thousands of people. While genetic testing is not a cure itself for disease, it has allowed researchers to better understand how various genetic components fit together and contribute to the onset of diseases. Here are recent discoveries in genetic testing:
- Breast cancer: One of the most advanced genomic tests for breast cancer is currently the Oncotype DX breast cancer test, developed by Genomic Health. The test works by using a sample of breast cancer tissue to analyze the activity of 21 genes, which can provide information on the likelihood of the breast cancer returning and whether and how much a patient may benefit from chemotherapy or radiation therapy. In April, Genomic Health reached two international milestones, as the BC Cancer Agency in British Columbia agreed to fund the Oncotype DX test for eligible patients. And in Germany, new guidelines recommended the test to predict benefits of chemotherapy in early-stage hormone receptor-positive invasive breast cancer.
- Prostate cancer: In April, scientists in Canada developed a genomic test that can identify patients with prostate cancer who are at an increased risk for recurrence after surgery or radiotherapy. Researchers said that the findings suggest that the genomic test can accurately predict whether certain treatments for prostate cancer will succeed or fail. With further research, the test may be able to tell doctors which patients will do well with surgery or radiotherapy and which patients will need further treatment beyond that.
- Psychiatric diseases: Unlike cancer, psychiatric diseases cannot be easily examined in the lab or in a petri dish or in mouse studies, but genomics is helping to change that. This month, Assurex Health announced an expansion to its GeneSight Psychotropic test, which works by collecting information on a patient’s genetic profile and drug response and metabolism genes for 38 psychiatric drugs. Experts said that the test can help doctors make individualized medication decisions for people with psychiatric disorders such as schizophrenia, depression, anxiety and post-traumatic stress disorder (PTSD).
Are there any limitations to genomic testing?
As the science community continues to make advances in genomic testing, there are also concerns about potential limitations and risks. One complexity involves the question of when patients should be told about incidental findings—such as a discovery that a patient’s genes show that he or she has a higher risk of a disease that wasn’t the reason for the testing. A similar complexity involves unexpected information about a patient’s relatives’ risk for disease or for having a child with a particular condition. Researchers have also expressed concern that because much of the human genome remains unexplored, there remain limits on how useful genomic sequencing can be in doctors’ offices, For example, in most cases, one in three or four cases typically results in the discovery of a genetic cause of a disease.
What’s next in the field of genomics?
Scientists have made much progress in pharmacogenomics, which involves using data on a patient’s genome to better individualize drug therapy to fit his or her needs. Much research in genomics, however, remains in the laboratory, and it will take time for discoveries to move into the medical clinic. For example, according to the National Human Genome Research Institute, most new drugs that may be developed based on genomics research are likely 10 to 15 years away. With more time and proper funding, however, researchers hope to not only better understand hereditary risks of complex diseases, but also be able to explain how various cellular components work together to affect the human body in disease and in health.