There is no longer a “one-size-fits-all” approach to cancer treatment. Even among patients with the same type of cancer, the behavior of the cancer and its response to treatment can vary widely. By exploring the reasons for this variation, researchers have begun to pave the way for more personalized cancer treatment. It is becoming increasingly clear that specific characteristics of cancer cells and cancer patients can have a profound impact on prognosis and treatment outcome. Although factoring these characteristics into treatment decisions makes cancer care more complex, it also offers the promise of improved outcomes.
Not all cancer cells are alike
Cancer cells may differ from one another based on what genes have mutations. Precision cancer medicine utilizes molecular diagnostic testing, including DNA sequencing, to identify cancer-driving abnormalities in a cancer’s genome. This “genomic testing” is performed on a biopsy sample of the cancer and increasingly in the blood using a “liquid biopsy”
Once a genetic abnormality is identified, a specific precision cancer medicine or targeted therapy can be designed to attack a specific mutation or other cancer-related change in the DNA programming of the cancer cells.
Precision cancer medicine uses targeted drugs and immunotherapies engineered to directly attack the cancer cells with specific abnormalities, leaving normal cells largely unharmed.
Precision cancer medicines can be used both instead of and in addition to chemotherapy to improve treatment outcomes.
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 (chemotherapy or precision cancer medicines) 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 if tissue is not available to perform genomic testing?
A: There are two options: an additional biopsy can be performed if feasible or an individual can consider a “liquid biopsy” A liquid biopsy is performed by testing a sample of blood for the presence of circulating cancer cells, known as circulating tumor cells. Samples of blood obtained from a liquid biopsy can also be tested for cell-free tumor DNA (cfDNA), which are fragments of DNA shed by cancer cells into a patient’s bloodstream.
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: Genomic testing is developing at a rapid pace. Established testing is particularly advanced in colon, lung and breast cancer where several precision cancer medicines have already been developed. Genomic testing is also increasingly playing an important role in individuals with rare cancers, cancer of unknown primary and those with widely metastatic disease.
Undergoing genomic testing that looks at expression across a wide variety of genes may identify certain genes that could potentially be a target for therapy that is otherwise not considered. A change to a precision cancer medicine would have the potential to markedly improve survival.
Further Reading and Other Resources
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