By Darren Wheeler, MD
Q: What is genomic testing?
A: Genomic testing looks at a group of genes and their varying levels of expression. This gene expression or activity can characterize how genes interact with one another and predict the behavior of certain tissues within the body. This is in contrast to genetic testing, which looks at a specific change within an individual chromosome or gene, often as part of an inheritable trait.
Q: What role does genomic testing play in a cancer diagnosis?
A: Genomic testing can provide information about a patient’s prognosis based on the gene expression within an individual’s cancer tissue and can often predict if certain therapy (such as chemotherapy) will be of benefit.
Q: At what point in the diagnostic process does genomic testing occur?
A: Genomic testing can occur at any time after a tissue sample (biopsy or resection) of cancer has been acquired.
Q. What questions should I ask my healthcare team about genomic testing?
A: The following are the primary questions to ask your healthcare provider.
- Is genomic testing available for the type of cancer I have, to aid in determining my overall prognosis?
- Will the results of this testing have the potential to change your management of the cancer? Specifically:
- Will the test be able to tell me if certain therapies will be of benefit in my treatment?
- Have you had positive outcomes in using this testing with other patients?
- Is this testing covered by my insurance plan? (This type of testing can run in the thousands of dollars, though many plans cover the tests without an out-of-pocket expense.)
Q: Are there specific cancer types for which the role of genomic testing is especially significant?
A: There are three types of cancer patients for whom genomic testing may be particularly advantageous:
- Patients with estrogen receptor–positive breast cancer that has not yet spread to the lymph nodes (early-stage breast cancer) may have a prognosis that is difficult to predict by tissue biopsy alone. Genomic testing may not only aid in providing prognostic information (i.e., predicted 10-year survival) but can also predict whether chemotherapy will be of any significant benefit, allowing a patient to avoid the toxicity of chemotherapy when possible.
- Patients with certain types of colon cancer can also benefit from genomic testing in terms of determining prognosis, predicting chemotherapy benefit, and selecting chemotherapy (determining which chemical agents will be of most benefit).
- Patients with a cancer that has spread to other sites of the body (metastatic disease) or that has recurred locally (despite surgery and/or chemotherapy) can undergo genomic testing that looks at expression across a wide variety of genes, including those not typically associated with the original site of cancer. This type of genomic testing can identify certain genes that may potentially be a target for therapy that was initially not considered. A change to a targeted therapy would have the potential to markedly improve survival.
Darren Wheeler, MD, is currently the west regional medical director for anatomic pathology for Quest Diagnostics in Las Vegas. He received his medical degree from and completed his residency in anatomic pathology at the University of Washington in Seattle and completed a fellowship in gynecologic pathology at The Johns Hopkins Hospital in Baltimore, Maryland. Before joining Quest Diagnostics, Dr. Wheeler served two years as a consultant for the Gynecologic and Breast Pathology Department at the Armed Forces Institute of Pathology in Washington, DC. He continues to perform subspecialty consultation for Quest Diagnostics in gynecologic and breast pathology and routinely performs cancer diagnostics on all solid tumors, including the processing of tissue samples for genomic testing.