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Cancer Genetic® Screening CGx©
Genetic testing looks for specific inherited changes (variants) in a person’s genes. Genetic variants can have harmful, beneficial, neutral (no effect), or unknown or uncertain effects on the risk of developing diseases. Harmful variants in some genes are known to be associated with an increased risk of developing cancer. These inherited variants are thought to contribute to about 5 to 10% of all cancers.
Cancer can sometimes appear to “run in families” even if it is not caused by an inherited variant. For example, a shared environment or lifestyle, such as tobacco use, can cause similar cancers to develop among family members. However, certain patterns that are seen in members of a family—such as the types of cancer that develop, other non-cancer conditions that are seen, and the ages at which cancer typically develops—may suggest the presence of an inherited susceptibility to cancer.
Genes involved in many of the known inherited cancer susceptibility syndromes have been identified. Testing whether someone carries a harmful variant in one of these genes can confirm whether a condition is, indeed, the result of an inherited syndrome. Genetic testing is also done to determine whether family members who have not (yet) developed a cancer have inherited the same variant as a family member who is known to carry a harmful (cancer-susceptibility predisposing) variant.
A different type of genetic testing, called tumor DNA sequencing, is sometimes done to determine if cancer cells of people who have already gotten a cancer diagnosis have genetic changes that can be used to guide treatment. Although some of these cancer cell changes may be inherited, most occur randomly during a person’s lifetime.
Genetic testing can identify people at higher risk for developing cancer. Genetic testing is currently available for more than 20 hereditary cancer syndromes and more than 50 hereditary cancer genes, and the list is growing.
Types of genetic testing for cancer include:
- Panel testing
- Single-site testing
- Specific-site testing
- Somatic testing
- Direct-to-consumer testing
Genetic testing can play an important role in the management of patients with certain cancers, as well as help inform preventative measures for family members who may be at risk of developing cancer.
Genetic testing for cancer can help the practitioner:
1. Select the best treatment options for patients; and 2. Determine appropriate screening methods for family members.
Hereditary testing for cancer also is referred to as germline testing. This form of GCx testing looks for germline mutations that signify the possible disposition to certain types of cancer.
Germline Mutation. A gene change in a body's reproductive cell (egg or sperm) that becomes incorporated into the DNA of every cell in the body of the offspring. Germline mutations are passed on from parents to offspring. Also called hereditary mutation.
Germline mutations are present in each cell. Germline testing is usually performed on blood or saliva. Types of cancer that are available for germline genetic testing include:
- Breast cancer
- Ovarian cancer
- Pancreatic cancer
- Skin cancer
- Kidney cancer
- Colorectal cancer
- Prostate cancer
Some patients may not yield reliable results from genetic testing. Two subsets of such patients are those who received bone marrow transplants and have hematologic malignancies:
Bone Marrow Transplant Recipients
- Bone marrow transplant recipients are known to express donor DNA in both blood and saliva. Therefore, genetic test results from blood or saliva of bone marrow transplant recipients are unreliable.
- If genetic testing is needed for a patient who has undergone a BMT, cultured fibroblasts are felt to be a reliable source of DNA. Blood and saliva samples should not be used for testing these patients.
Patients with Hematologic Malignancies
- Patients with current hematologic malignancies (e.g., leukemia or myelodysplastic syndrome) have an increased laboratories will not typically accept blood samples from these patients.
- Cultured fibroblasts or fresh/frozen normal tissue may be an option. Specific limitations and requirements should be discussed with a genetic counselor and testing facility prior to testing.
Billing for CGx
Germline genetic testing for common high-risk hereditary cancer genes is covered by most insurance plans; however, most insurance plans do have family history criteria (as is the case currently for BRCA, Lynch, and FAP testing). The criteria are typically modeled after national guidelines (NCCN) although it might not be up to date with current guidelines and each insurance company is different. A patient must meet his or her insurance's criteria for a given gene for that test to be covered.
Other aspects of billing and insurance to consider include:
- Most insurance companies do not yet have criteria to determine coverage for genes besides BRCA, Lynch, and FAP. This includes other hereditary cancer syndromes and moderate-risk cancer genes.
- Individuals may have coverage for NGS panel testing if they meet criteria for multiple genes on the panel. Other insurance companies have genetic testing exclusions or limits on the number of genetic tests in a lifetime.