Genetic testing is the analysis of genes, chromosomes, and proteins. It is used to predict the risk of disease, identify carriers (individuals who do not have the disease but have a copy of the disease gene) of disease, diagnose disease, or determine the likely course of a disease. More than 900 genetic tests are available for many different diseases, including breast, ovarian, colon, and some rare cancers.
Genetic testing for cancer risk is predictive testing, which means a test can help predict the likelihood that an individual will develop cancer in his or her lifetime. No genetic test can report with 100% certainty that a person will develop cancer, but the tests can tell a person if he or she has a higher risk of developing cancer than the general population. Not everyone with a cancer-related gene will develop cancer. For example, a woman with a 75% chance of developing breast cancer may remain healthy, while a woman with a 25% chance of developing breast cancer may eventually develop cancer.
The following factors suggest that a person may be at risk for developing a hereditary cancer:
ASCO recommends that genetic testing be offered in the following situations:
In addition, ASCO recommends counseling both before and after the genetic test. Learn more about ASCO's Policy Issue on Genetic Testing for Cancer Susceptibility.
Genetic testing can help a person (and in some cases, the family) understand the cause of cancer and the risk of developing cancer in the future or passing it on to children. Deciding to be tested is a personal decision that should be made in collaboration with your family and doctor. Someone may choose genetic testing for the following reasons:
To make a medical intervention. People at a higher risk for cancer may have the option of having more frequent cancer screenings, avoiding specific risk factors, making lifestyle changes to lessen additional risk, or taking preventive medication (chemoprevention), if available. In a few cases, people with a genetic predisposition to develop cancer may have the opportunity to reduce their risk. For example, women with either breast cancer susceptibility gene (BRCA1 or BRCA2) may reduce their risk of breast and ovarian cancer with a preventive salpingo-oophorectomy (removal of the fallopian tubes and ovaries).
To relieve anxiety. If a person has multiple family members who have cancer that can be traced to a genetic mutation, then a negative test result (meaning there is no mutation) may give this person a sense of relief.
Genetic testing has limitations and psychological implications.
Testing may cause depression, anxiety, or guilt. If a person receives a positive test result (meaning a mutation exists), it may cause anxiety or depression about the possibility of developing cancer. Some people may start to think of themselves as sick, even if they never develop cancer. If a person does not have the mutation when other members of the family do, this individual may experience guilt.
Testing may cause family tension. In some situations, a person may feel a responsibility to tell extended family members that they have a positive test result and encourage them to be tested. This process may lead to tension in the family.
Testing may provide a false sense of security. Just because a person's genetic test result is negative does not mean that person will never develop cancer. It only means his or her risk is equal to the risk of the general population of developing cancer.
Testing may provide unclear results. A person's gene may have a unique mutation that is not known to affect cancer risk. Or, the gene may have a mutation that is not detected by the available test. In either case, it may be impossible to calculate the risk of the mutation as it relates to cancer, which may lead to anxiety and uncertainty.
Testing is costly Genetic testing and counseling can be expensive, especially if it is not covered by insurance. Some people pay for testing "out of pocket" because they do not want their insurance providers to know that they have been tested.
Testing may cause confidentiality concerns. Results of genetic tests may be placed in a person's medical record, where there is a chance that this information could be passed on to insurance companies or employers. Some people fear that their test results may lead to genetic discrimination. Many people who undergo genetic testing are concerned about maintaining the privacy of their genetic information. They may be unsure if they want to share test results with immediate relatives and are concerned about employment and health insurance discrimination, which could result in the loss of a job and/or insurance coverage. Consider discussing privacy concerns with a genetic counselor or doctor.
Before being tested, be sure you have a complete understanding of the risks of testing and your reasons for wanting a test. It is also helpful to think about how you will cope with the results of the test. The following are some factors to consider in your decision making.
A genetic counselor can help address these issues. Genetic counselors are professionals specially trained to advise people about the risks and benefits of genetic testing and can help people through the process of testing and interpreting the results.
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