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Genetic testing is typically done only if you and your health care team feel that it’s the best thing for you and your family. Several steps are taken before actual testing is done. The entire process might involve 1 to 3 visits or phone calls.
The first step in genetic testing is to collect information about your personal and family medical history. This may be done by a genetic counselor, or a doctor or nurse trained in genetic counseling.
You will be asked about your own medical history. This may include biopsies or surgeries you have had, cancer screening tests, gynecologic history (for women), lifestyle factors, and exposure to things that can cause cancer (carcinogens). If you have been diagnosed with cancer, information such as the type of cancer, whether it has any relevant biomarkers, and if you’ve had more than one type of cancer, can also be important.
A detailed review of your family medical history is also important. Often, you will be asked to complete a questionnaire before your appointment, since you might need to ask relatives for information. The questionnaire will ask about how many relatives have had cancer on your mother’s and father’s side, including the type of cancer and their age when they were diagnosed. This can help determine if there is a pattern of cancer that might suggest a hereditary cancer syndrome. This is why it’s important to confirm the illnesses in your family by medical records and/or death certificates whenever possible.
Once the information about you and your family has been collected, the genetic counselor or other trained professional will go over this information to help determine:
Sometimes, a test looking at only one gene might be recommended, while at other times testing for a panel or group of gene changes might be better. The genetic counselor can explain the reasons for their recommendation.
At one of the visits, the genetic counselor will explain how families can inherit increased cancer risk and how genes are passed on. The risks, benefits, cost, and limits of genetic testing will be discussed, as well as who in the family should consider being tested. It is often a person who has or had cancer. Sometimes, more than one family member may be offered testing.
You will want to think about how the results might affect you and your relatives, and discuss these issues with the counselor before testing.
For example, if testing shows that you have a high cancer risk, the counselor may also talk about the best ways to manage it. These may include lifestyle changes, early detection, watching for signs and symptoms of cancer, medicines to reduce cancer risk, or even preventive surgery.
Many of these issues require the skills of an expert counselor. An increased risk of cancer, especially for children, and the potential for discrimination can be frightening. It often helps to discuss your family’s attitudes about cancer and the possibility of a family member being “blamed” for the cancer. You may also talk about how cultural beliefs, support systems, and finances may play a role in how your family views cancer.
The counselor will explore ways to help you cope with the results of genetic testing, as well as help to ease your specific fears and concerns. The counselor can also help you with how to discuss the test results and what they mean with other family members.
It’s important to check with your health insurance company to find out if genetic counseling and genetic testing will be covered. Your genetic counselor may be able to help you find out if the recommended test(s) is covered.
Remember that genetic testing is your choice. Even if the counselor recommends you be tested (or even if the counselor tells you genetic testing might be helpful for you), you still have the right to refuse it.
After risk assessment and genetic counseling, you can decide if you want to proceed with testing. Some people prefer to go home and think about it first, but others are ready to complete testing that day. If you decide to be tested, you’ll be asked to give your informed consent in writing. The process of informing you and your family about testing should cover:
For more on this process see Informed Consent.
Once you’ve signed the consent form, lab tests are done on cells taken from your body. Genetic tests for cancer are typically done on a sample of blood, saliva (spit), cheek cells (from swabbing the inside of your mouth), but they can also be done on other body tissues. Those who have an active blood cancer (such as leukemia) or a history of a bone marrow (stem cell) transplant may need to give a sample other than blood or saliva for accurate results. Typically, there are no dietary restrictions before this type of test.
Be sure to ask your genetic counselor when to expect the test results, and if you need to schedule a follow-up appointment to discuss them.
Once the results are ready (often 2-3 weeks later), your genetic counselor will share the results with you. This may be by phone or at a scheduled appointment. You might want to ask for a copy of the test result for your records if one is not given to you. Some people might choose to have a family member with them when they get their results. This might be for emotional support, to help make sure they understand the information, to help with asking questions and taking notes, or to help share results with other family members.
Testing does not always give you clear answers, but genetic counselors are trained to interpret and explain the test results and what they might mean to you and your family.
The results of each test might come back as:
A positive result means you have a mutated gene (or genes) that may place you at higher risk for developing certain types of cancer. If you have already been diagnosed with cancer, the result might have found a factor that played a role in causing the cancer. It might also suggest a higher risk for developing other cancers.
Many people are concerned or anxious after learning they are at increased risk for cancer. This is normal. The results may also point toward a higher risk for certain family members, which can be stressful. Concern about being treated differently may also become more real.
Even after the testing is complete, there might still be a lot of uncertainty. In most cases, there’s no way to know for sure if or when cancer might develop. But it’s important to remember that the results of genetic testing do not change your current state of health, meaning they do NOT tell you if you have cancer or not. Your health care provider or counselor can help you sort through your options at this point, including what you might be able to do to lower your risk of these cancers or catch them at an early stage. (See “What if genetic testing shows an increased cancer risk?” below.)
The counselor will talk to you about whether your family members might also be affected. It will be important for those family members to know exactly which mutation was found, so they can decide if they want to be tested for it as well. To make sure family members are tested correctly, you might want to share a copy of your actual test results with family members interested in genetic testing. They can then discuss this with their health care providers and might decide to get tested, too.
A positive result could also mean that you have a mutated gene (or genes) that may affect your treatment options for certain types of cancer.
If the test result is negative, it means the test did not find a mutation in the genes it tested for.
If you have a family history of a known gene mutation, knowing you don’t have this mutation can be very comforting. But it doesn’t mean your risk of cancer is zero. It just means you have the same average risk as most other people.
Family members with negative test results may feel guilty if other family members test positive. Your health care provider or genetic counselor can help you understand what the test results mean for you and your family and how to deal with them.
If there is no known gene mutation in the family, a negative result can still be helpful. It means you don’t have that specific mutation (or any of the other mutations that might have been tested for). But genetic testing doesn’t look for every possible gene mutation, so you can also get a negative test result if:
Understanding what a negative test result means for your cancer risk and what you can do next to help lower your risk is one of the more complicated elements of genetic counseling. Depending on your situation (such as your family cancer history), you and your family might still be considered at high risk of cancer even with a negative test result. This is why it is important to discuss your negative result in detail.
When a genetic test shows that a person has a change in a gene, but it’s not known if this gene change affects cancer risk, it is reported as a variant of uncertain significance (VUS). It may be a normal variant, simply a different version of a gene that isn’t seen often enough to be sure, or there may be some other explanation for it.
Your genetic counselor can help you understand what a VUS result might mean for you and your family. Typically, no changes to your medical care are recommended when a VUS is found because most VUSs are later found to be benign (causing no medical harm) once more information on them becomes available.
For some people, a VUS result can cause anxiety, frustration, and even anger because the result isn’t clear and there is no exact timeline on when it might become clear. You usually don’t need to have repeat testing if you have a VUS, but staying in contact with the healthcare provider who ordered the test is important in case updates on the VUS become available.
If your genetic test result is positive for a gene mutation that could increase your risk of cancer, managing your risk should become a priority.
Depending on which type(s) of cancer you are at increased risk for, some of the ways you might lower your risk or find cancer early include:
Your health care provider may recommend one or more of these approaches, but it’s important to understand how much they could lower your risk before you decide on a course of action. You will also want to be sure you understand their risks and benefits before deciding on a plan. These approaches are discussed in more detail below.
Ask your health care provider about lifestyle changes you can make that could help lower your cancer risk. For instance, avoiding or limiting alcohol use and getting regular physical activity can help lower your risk of colon and breast cancer, while not smoking lowers the risk for a number of cancers.
In some cases, the effects of these changes on risk might be small compared to the increased risk from the mutation, but you may still want to ask your provider what you can do.
Chemoprevention is the use of medicines to help keep cells from developing into certain types of cancer. It is not the same as chemotherapy. These medicines are used to help lower the risk of certain cancers in people known to be at high risk. For example, tamoxifen and drugs called aromatase inhibitors are pills used mainly to treat people with breast cancer. But these drugs have also been shown to help lower breast cancer risk in people at high risk.
Each person’s risk and medical situation must be considered carefully so that any harmful effects of the drugs do not outweigh the benefits. As we learn more about the genetics of cancer, we hope to learn more about using medicines to help lower cancer risk as well.
Prophylactic (preventive) surgery is another option in some cases. For example, some women at high risk for ovarian cancer might decide to have their ovaries removed once they’ve had their children, which can greatly lower their risk. This can be important because screening tests are not considered reliable for this cancer, and many women do not have symptoms when the tumor is early stage.
Often, those with a positive genetic test result will get different screening advice than for those at average risk for that cancer type. Early detection (screening) tests may be recommended to start at an earlier age and/or be done more often, or along with additional tests. For instance, a person known to have an increased risk of colon cancer might need to start screening earlier than usual. Likewise, a woman with a genetic mutation that raises her risk of breast cancer might need breast MRI scans along with her mammograms to look for early signs of the cancer.
But it’s important to understand that many people with negative results might also get special screening recommendations based on their personal or family history of cancer. This is another reason why speaking with a genetics expert can be important for determining a care plan.
It’s also important to be aware of the possible signs and symptoms of cancers you are at higher risk for, and to see a doctor right away if anything concerns you. Finding cancer early – when it’s small and has not spread – offers the best chance of treating it successfully.
If you have a positive test result (a gene mutation that raises your risk), you may need to think about sharing the information with other family members who might also be at increased risk. This information could possibly be life-changing, because telling them might help them decide if they should also get genetic counseling and testing and/or adopt some of the approaches to try to lower their own risk.
Genetic test results can also cause anxiety, and some family members may not want to know their risk. This is especially true if there’s not much they can do with the results. You might want to speak with family members before you get tested to find out if they want to know your results.
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
Bonadies DC, Farmer MB, and Matloff ET. Chapter 38: Genetic counseling. In: DeVita VT, Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg’s Cancer: Principles & Practice of Oncology. 11th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2019.
Centers for Disease Control and Prevention. Genetic Testing. June 24, 2022. Accessed at https://www.cdc.gov/genomics/gtesting/genetic_testing.htm on August 19, 2022.
MedlinePlus [Internet]. Bethesda (MD): National Library of Medicine (US); [updated 2020 Jun 24]. Help Me Understand Genetics; [updated 2020 Jun 18; reviewed 2018 Jun 01]; Available from: https://medlineplus.gov/genetics/understanding/.
National Cancer Institute. The Genetics of Cancer. August 17, 2022. Accessed at https://www.cancer.gov/about-cancer/causes-prevention/genetics on August 19, 2022.
Last Revised: September 14, 2022
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