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Before Undergoing Genetic Testing for Cancer

Testing for mutations in genes that give an increased risk for cancer is complicated. Below is a description of concepts that are important to understand when considering genetic testing. You may wish to speak with your doctor or health care provider, or obtain a referral to a genetic counselor, to find out about specific testing availability applicable to your situation. Because your family members may be affected by test results, you may want to think about speaking with them about genetic testing as well.

Inquire about lab testing methods

Testing methods vary from lab to lab and may affect the likelihood that the lab will identify a mutation in the gene if a mutation is present. Different lab studies have the ability to detect different types of mutations. Accuracy will vary, depending on the method of testing done. Sometimes the type of tissue studied (tumor vs. blood sample, for instance) also affects the likelihood of finding a mutation. Also, some families may have a mutation in a gene, but the mutation is not detectable with current technology. In these cases, genetic testing may give a false-negative result--one that indicates a normal result when there actually is a problem. But many genetic tests are offered by a single  lab, usually the one that developed or licensed the test. 

Not all people with what appears to be an inherited cancer will have a mutation. Reasons for this include:

  • The accuracy of testing is not 100%, and the tests may not look for less common mutations.

  • Testing is not available for all genes associated with a hereditary cancer.

  • A mutation is present in the family, but no test is yet available to identify it, or a particular mutation has not yet been discovered.

  • The person tested has developed cancer through a nongenetic mechanism (it's a sporadic case that develops randomly), while the other cases in the family are because of a mutation.

  • The family does not have inherited cancer in spite of a clinical presentation that suggests a genetic basis. This may occur as a result of incorrect reporting of cancer diagnoses in the family or if cancer developed in several family members independently.

If genetic testing is done and no mutation can be identified in an affected family member or members (the ones with cancer), testing unaffected relatives for the same gene will not help in clarifying cancer risks.

In this situation relatives of the affected person would remain at increased risk of developing cancer by virtue of their family history. They may need to be tested with a full available panel of mutation tests.

Consider the implications of testing results

If a person is mutation positive:

  • The likelihood of developing various cancers depends on the gene in which the mutation is found and in some cases, where in the gene the mutation is located.

  • Other genes and environmental risks factors may modify cancer risk.

  • Test results give a probability, but not a certainty, of cancer development and do not tell you when cancer may develop or the stage or grade of a potential tumor.

  • Test results may help you be proactive about cancer surveillance or preventive measures.

  • Some test results may not change recommendations for medical management or cancer surveillance, but others may have an immediate impact. Ask your doctor whether positive test results will change your management or surveillance program. 

If a person is mutation negative:

  • If there is a known mutation in the family, then he or she is not at increased risk of developing cancer based on family history but is at general population risk. If the person tested belongs to a particular ethnic group where common mutations have been identified, then relatives should consider testing for all ethnic-specific mutations, not just the one present in the family.

  • If there is not a known mutation, a negative test result is uninformative. The family may have a mutation in the gene tested that is not detectable with current technology or a mutation in a different gene, since many cancer syndromes are genetically heterogeneous (caused by mutations on one of several different genes).

If a variant of uncertain significance is found:

  • In this case, an alteration in the DNA of a gene has been identified, but it is unknown whether the alteration will actually affect the function of the gene or influence cancer risk. Further studies may be indicated to look for other mutations or whether there may be two independent mutations that may interact. If a significant family history is present, such a result does not rule out a hereditary cancer syndrome in a family.

Consider the psychosocial implications of testing

You may become newly worried, or relieved after testing for mutations in cancer susceptibility genes. Relationships with family members may change, particularly if one person is mutation positive, while another is mutation negative. Some people feel guilty when they are the only person in their family without a mutation or if they feel that they gave a mutation to a family member. Some relatives may deny the results or blame the person for bringing the "bad news," or refuse to be tested, even if that will help the person's testing process. Communication between family members can improve or stop altogether, depending on test results. It is important to try to anticipate potential problems in the family related to testing before proceeding.

Consider the economic impact

Testing for cancer susceptibility genes may not be covered by insurance and can be costly. Check with your insurance company about coverage prior to having testing performed. Some lab do testing for free or for a nominal fee if you are part of a research study. Additionally, programs are sometimes available to assist with covering the cost of genetic testing, depending upon the lab.

Consider the risks of genetic discrimination

Many people are concerned about the risk for genetic discrimination. Genetic discrimination means that a person is discriminated against based on his or her genetic information alone. An example of genetic discrimination would be if an insurer were to increase your premiums because it found out you carry a mutation that increases your risk of developing cancer, even though you do not currently have cancer and may not develop the disease.

On the federal level, the Genetic Information Nondiscrimination Act of 2008 prevents health insurers and employers from discriminating against people based on their genes. Most states also have laws regulating the use of genetic information by medical insurance companies.

Remember that testing options change

Remember that technology is rapidly advancing. If you are a person for whom no testing currently exists, testing options may become available in the near future.

Take your time

Do your homework and be sure to take the time to explore the above issues before undergoing testing for mutations in cancer susceptibility genes, in order to fully understand the implications of your test results. Remember, genetic testing is a personal choice, and is not for everyone. Only you can decide what is right for you.