Genetic Testing for Cancer Risk
What is genetic testing for cancer risk?
In cancer, genetic mutations change how our cells work, particularly how they divide and multiply. The majority of these mutations happen during a person’s lifetime. Sometimes, though, people inherit mutations that put them at increased risk of developing an inherited (hereditary) cancer. Hereditary mutations cause about 5% to 12% of all cancers. Healthcare providers typically do genetic tests (DNA tests) to confirm someone has an inherited (hereditary) cancer.
If genetic tests show you have a hereditary mutation that increases your cancer risk, your healthcare provider may recommend that your family members have the same tests. Genetic testing for cancer may have significant medical, financial and psychological implications. If you’re going to have a genetic test for cancer, you should work with genetic counselors before the tests so you understand all the ways genetic testing for cancer may affect you and your family.
How do genetic mutations cause cancer?
Genetic mutations that lead to cancer change your DNA. Your DNA is responsible for building and maintaining your human structure and is organized into genes. Your genes contain instruction manuals for making proteins. Proteins control millions of actions, including how cells grow and multiply.
Mutations that change the instructions needed to make certain proteins can turn healthy cells into cancerous cells. For example, the TP53 gene has the instruction manual for making a protein called tumor protein 53, or P53. This protein keeps your cells from dividing and growing too quickly or in an uncontrolled way so they become tumors. When your TP53 gene mutates, it loses or changes the instruction manual for making protein 53. Without properly functioning P53 proteins, cells can divide uncontrolled and become cancers.
What genetic mutations cause cancer?
Cancer may happen when a single gene mutates or several genes that work together mutate. Researchers have identified more than 400 genes associated with cancer development. Many of these genes can cause an increased risk of cancer if they’re inherited. Examples include:
- Inherited breast and ovarian cancer syndrome: People who inherit mutated forms of BRCA genes have an increased risk for breast cancer, ovarian cancer and other cancers.
- Lynch syndrome: This inherited condition increases colorectal (colon) cancer risk and several other types of cancer. Lynch syndrome happens when one of five genes that repair DNA mutates.
- Li-Fraumeni syndrome: This rare inherited condition happens when the TP53 gene mutates. TP53 genes help control cell growth.
Tumor suppressor genes are among the most common genes linked to cancer. Normally, tumor suppressor genes code for (make) proteins that fix damaged DNA or keep cancerous cells from multiplying.
Tumor suppressor genes put the brakes on cancer cell growth. When these genes mutate, it’s as if they switch from keeping a foot on a vehicle’s brakes to putting a foot down on a vehicle’s gas pedal. When tumor suppressor genes mutate, the cancer cells they’re supposed to keep under control start multiplying uncontrollably to become tumors.
What cancers can be caused by a hereditary mutation?
Hereditary mutations can cause a wide variety of cancers. Common forms of these cancers include breast cancer, ovarian, colon, uterine, pancreatic and prostate, stomach, thyroid and kidney cancers. Not all cancers are hereditary. For example, cervical cancer isn’t hereditary.
Who should have genetic testing for cancer risk?
According to the National Cancer Institute, factors that may indicate you would benefit from having genetic testing for cancer risk include:
- You were diagnosed with cancer before age 50.
- You have several different kinds of cancer.
- You have cancer in both sets of an organ, such as cancer in both of your kidneys or both breasts.
- Several first-degree family members have the same type of cancer. First-degree family members include your biological parents, siblings or children. Some researchers advocate for testing second-degree and third-degree family members.
- Several of your family members have or have had cancer.
- You have a specific cancer type that usually doesn’t happen in people your age or sex. Breast cancer in a man or person designated male at birth is an example of an unusual instance of a specific cancer type.
- You have physical differences linked to certain inherited cancer syndromes. For example, neurofibromatosis Type 1 is an inherited cancer that also causes other symptoms such as noncancerous tumors called neurofibromas.
- You’re a member of a racial or ethnic group that’s known for having certain inherited cancer syndromes AND you have one or more of the factors listed above. For example, studies show BRCA1/2 mutations are more common in people who are of Ashkenazi (Central and Eastern European) Jewish ancestry.
What are the benefits of genetic testing for cancer?
In genetic testing for cancer, knowledge may take away some anxiety or fear of the unknown. A person with an inherited cancer may receive specific cancer treatment because genetic testing showed they carry mutated genes linked to that cancer. Additionally, the person and their healthy family members carrying the same hereditary mutation can work with healthcare providers on ways to prevent cancer from happening. A person with inherited cancer can take steps so they don’t pass their hereditary mutation on to their biological children.
What are the disadvantages of genetic testing for cancer?
Researchers studying the impact of genetic testing on families have found genetic testing can cause psychological distress (such as anxiety and guilt) and affect family relationships.
People with inherited cancerous genes may worry other people — friends, employers, insurance companies — may learn about their situation. People who may have inherited cancerous genes may worry about the possible costs of paying for genetic testing and follow-up tests.
How is genetic testing for cancer done?
Genetic counseling is the first step in genetic testing. Healthcare providers typically recommend genetic counseling before they do any genetic testing. Trained genetic counselors typically discuss the following topics as part of genetic counseling:
- Whether genetic testing is appropriate in the given situation.
- Explanation of the specific tests that may be used.
- The potential benefits and harms of testing.
- Test expenses.
- The medical implications of test results.
- Impact of testing on family, including the risk of passing genetic mutations on to biological children. The possibility that testing may find a genetic mutation that medical researchers can’t say if it will increase cancer risk.
What are types of hereditary genetic tests for cancer?
Hereditary genetic cancer tests include:
- Single mutation: This test looks for changes in a specific area of a single gene. Healthcare providers typically test family members when someone in the family has a known specific genetic mutation.
- Single gene testing: This test looks at the entire DNA within a specific gene.
- Panel tests: These tests look for mutations in several genes.
How do healthcare providers do genetic testing for cancer?
In genetic testing for cancer, healthcare providers typically collect a sample of your blood or saliva that they send to a laboratory. At the lab, technicians will look for changes in your genes. The technicians send the test results to your healthcare provider. While taking blood takes little time, providers may need days or weeks to complete test analysis.
Is genetic testing for cancer accurate?
Genetic tests are a very reliable way to find mutations that may increase your risk of cancer. Again, it’s important to keep in mind that test results can’t state if you’ll definitely develop cancer. These tests show if you carry a mutated gene linked to certain cancers. Genetic tests may not find all mutated genes, or they may find a mutation that may or may not affect the gene in question.
Is genetic testing for cancer expensive?
Costs depend on several factors such as your personal and family history and the test ordered. In general, genetic tests may cost a few hundred dollars up to a few thousand dollars. Health insurance often covers some or all costs depending on your personal and family history of cancer. If you’re considering genetic testing for cancer, ask your genetic counselor to outline potential options and costs.
Results and Follow-Up
What results would I get from genetic testing for cancer?
Genetic tests can have several possible results: positive, true negative, uninformative negative or benign.
This test result means you have a genetic mutation that’s linked to a specific inherited cancer. Positive results have different implications depending on why you were tested.
- If you have cancer, a positive test result confirms you have cancer because you inherited certain genetic mutations. It’s important to remember that your test result doesn’t mean your family members have the same mutation, that they must have genetic testing for cancer or that they’ll develop cancer.
- If you had genetic testing because a family member has an inherited cancer, a positive test result means you have an increased risk of cancer. It doesn’t mean you’ll develop cancer. If you have a positive test result, your genetic counselor will explain what the results mean. They or your healthcare provider may give you information on ways to lower your risk of developing cancer.
This result means the test didn’t find a mutation associated with an increased risk of cancer. If you have cancer and your genetic test for a certain genetic mutation shows you don’t carry that genetic mutation, it means your cancer isn’t inherited. It also means your family members don’t need to have genetic testing.
If there’s a known mutation in your family, your negative result is a true negative. This means you don’t carry the genetic mutation that increases your family members’ risk of developing cancer. True negative results don’t eliminate all cancer risks. You may still develop cancer, but your risk is the same as any other person in the general population.
If there’s no known mutation in your family but someone in your family has cancer, healthcare providers classify negative results as uninformative negative. You still may be at risk of developing cancer and your provider may recommend you have increased cancer screening,
Variant (mutation) of uncertain significance or VUS
Medical researchers haven’t identified all genetic mutations that may increase the risk of cancer. That means it’s possible you could have a genetic mutation that hasn’t been associated with an increased risk of cancer or that is just part of normal human variability.
Healthcare providers don’t use VUS when making recommendations, but a person with a VUS result should keep in touch with their provider in case additional research identifies a link between the VUS and a specific inherited cancer.
A benign variant is a common genetic change that doesn’t cause cancer.
What happens next?
If tests show you have an inherited cancer, your healthcare providers will use what they’ve learned to tailor treatment. Genetic counselors will be glad to help you explain your situation to family members.
If your family members were tested, they’ll meet with genetic counselors to review their test results. Counselors will explain test results and options. They’ll do everything they can to help your family feel comfortable with their decisions about genetic testing.
A note from Cleveland Clinic
In a way, genetic testing for cancer may be a mixed blessing. If you have an inherited form of cancer, genetic testing confirms your diagnosis and helps healthcare providers plan treatment. If your family members are worried about their cancer risks, genetic testing may eliminate some of their concerns. But genetic testing for cancer can affect family relationships by creating anxiety, fear and tension. Healthcare providers — particularly genetic counselors — understand how genetic testing for cancer affects family dynamics. Having to cope with cancer already puts pressure on you and your family. You and they’re already dealing with big challenges. Ask your genetic counselor or healthcare provider for help if you think your family is struggling with the idea of genetic testing or test results.
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