Genetic testing for inherited cancer predisposition is typically performed by testing for 1 condition at a time. For example, as discussed in the June issue of The Oncology Nurse-APN/PA, an individual with lobular breast cancer and a family history of breast and abdominal cancers may undergo testing for the BRCA genes and, if negative, then have the CDH1 gene analyzed. However, with the tremendous advances in genetic testing technologies over the past few years, the cost of testing has plummeted. To put this into perspective, the first human genome cost $2 billion to $3 billion to sequence and took over 10 years to complete. Today, the cost of sequencing a human genome would be less than $10,000 and would take 4 to 6 weeks to complete. Some predict that the cost may be less than $1000 by the end of 2012.1 As such, it has become realistic to test for multiple inherited cancer conditions at the same time using cancer panels.
What Are Cancer Panels?
Cancer panels utilize a technology referred to as next-generation (nextgen) sequencing, which allows multiple genes to be analyzed simultaneously for mutations at a cost comparable to testing for a single inherited condition. The particular genes on a panel vary depending on the laboratory performing the test. So far, laboratories appear to be designing their panels specifically for cancer genes associated with a single or a few cancer types. For example, a breast panel includes genes known to predispose to breast cancer, and a colon panel includes genes known to predispose to colon cancer. Because some genes convey an increased risk for both breast and colon cancer, these genes would be included on each panel. To date, insurance reimbursement for testing has been encouraging.
When Should Cancer Panels Be Utilized?
Many factors go into determining a genetic testing strategy. Therefore, no single strategy would be appropriate for all patients. A general guideline is that if a family history does not appear consistent with a particular cancer syndrome, a cancer panel including all or the majority of genes in the differential diagnosis may be useful.
Are There Limitations/Challenges Associated With Cancer Panels?
Multiple studies have demonstrated that the majority of healthcare providers do not have adequate knowledge of genetics and are deficient in taking family histories, ordering the correct genetic testing, and/or interpreting genetic test results. However, despite these deficiencies, professional guidelines, technologic advances, and consumer demand continue to increase the use of genetic testing. Therefore, at first glance, a colon panel that includes genetic testing for all the high-risk syndromes listed in the National Comprehensive Cancer Network guidelines for which clinical testing is available (such as Lynch syndrome, familial adenomatous polyposis, MYH-associated polyposis, Peutz-Jeghers syndrome, juvenile polyposis syndrome, hereditary diffuse gastric cancer, and Li-Fraumeni syndrome) may seem like the perfect solution. However, other issues to consider are the higher likelihood of receiving “variant of uncertain significance” (VUS) results and the need for these patients to be managed by providers versed in medical management of these syndromes. Additionally, some of the panels include genes associated with a moderate increase in cancer risk (at times based on inconsistent data), which further compounds the complexity in delivering results. Because testing for mutations in these genes was rare prior to the availability of next-gen sequencing technologies, approach and data surrounding their cancer risks and corresponding medical management options are limited.
Another potential issue influencing use of these tests is gene patents. For example, the BRCA1 and BRCA2 genes are patented, and laboratories offering breast panels cannot include the genes on their panel. Therefore, although a breast panel might be the most cost-effective approach for a patient with a diagnosis of breast cancer and a family history of abdominal cancer, a provider cannot currently perform both tests at one time. He or she would need to perform a breast panel first and then send to Myriad Genetics for BRCA testing, or start with BRCA testing and, if negative, then send a sample to a laboratory offering a breast panel. Although current research, insurance coverage, and clinical uptake of cancer panels appear promising, these tests are in their infancy, and research studies are needed to determine how best to utilize them in clinical practice and to educate healthcare providers.
Where Can I Obtain More Information About Cancer Panels?
As with any genetic test, providers should contact a number of laboratories to determine which laboratory best meets the needs of their patients. Keep in mind that the genes analyzed on a particular panel (such as a breast panel or colon panel) may vary by laboratory, as does turnaround time, experience interpreting VUS results, and billing procedures. Your local genetics provider should be able to provide you with additional information. Laboratories offering cancer panels include:
Ambry Genetics: www.ambrygen.com
City of Hope Laboratories: www.cityofhope.org
University of Washington Medical Center: http://depts.washington.edu/labweb/Divisions/MolDiag/MolDiagGen/index.htm
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