Genetic testing is not for everyone, but for people with a family history of particular types of cancer, genetic tests can help predict the risk.
When updating my book, Making the Chemotherapy Decision, I looked into the factors involved in making a decision to undergo genetic testing. Genetic testing triggered a recent double mastectomy by movie star Angelina Jolie which she undertook to reduce her cancer risk.
All cancers spring from cell mutations. It is now believed that from 5-10 percent of all mutations are inherited.
According to the National Cancer Institute, more than 50 hereditary cancer syndromes have been described. For some types of breast, ovarian, prostate and other cancers, an analysis of an individual’s genetic makeup may indicate the risk of developing future cancers. Genetic tests reveal only the likelihood of developing certain serious types of cancer, not the absolute certainty of contracting cancer, and not the age at which it might develop.
For example, the BRCA1 gene’s role in the body is to repair defective DNA. According to a meta-analysis published in the Journal of Clinical Oncology, women found to have a defective BRCA1 have a 57 percent risk of developing breast cancer by the age of 70 and a 40 percent risk of developing ovarian cancer by that age, as well as an increased risk of secondary cancers. The BRCA1 gene is quite rare, but its presence shows an increased risk for cancer and a need for preventive measures.
Genes inhabit every cell in our body. Genetic testing typically involves taking a sample of blood or saliva and sending it to a laboratory. At this writing, 38 clinical laboratories in the United States offer testing for particular genetic syndromes. Costs range from $200 to $3,000, depending on the laboratory and the test.
Genetic testing should not be done by everyone. Experts recommend genetic testing for cancer risk only when you have a personal or family history that suggests a risk condition, when test results can clearly tell you whether a particular genetic change is present or not, and when the results can provide information to you that will actually help guide your future medical care.
Genetic counseling with a trained professional such as a doctor or genetic counselor is strongly recommended before genetic testing. A professional can determine the appropriateness of testing, and explain the risks, and benefits, and limitations of particular tests. When deciding whether to have a genetic test, an extensive history of cancer on both sides of your family is crucial to the process. A professional can review your family history and assess whether testing is appropriate and of possible value.
When testing is considered, the psychological risks and benefits of particular test results should be discussed. While some test results can be clearly positive and show a particular mutation, or clearly negative and show the lack of particular genes, test results may also be inconclusive. In some cases, genetic testing is not useful at all.
A positive test result, if it comes, can be psychologically overwhelming. Test results of this type can provide a measure of relief or create enormous stress. A positive test result can lead to difficult long-term decisions, such as whether to have an ovary removed to lessen the risk of ovarian cancer, which makes having more children impossible.
If a positive result indicates an increased risk of developing a particular cancer, the risk of a serious cancer may be reduced in several ways. One is by being checked for cancer at a younger age, and checked more frequently. This is generally accepted practice. However, a study in the Netherlands found that annual screening of women for ovarian cancer had no efficacy.
A second way to reduce cancer risk is by changing personal behaviors. Quitting smoking, eating a better diet, and getting more exercise greatly reduce the risk of particular cancers.
The third and most drastic step is to take medication that may reduce cancer risk. For example, the antihormonal chemotherapy drugs tamoxifen and raloxifene are being administered to women with a particular genetic makeup who are at risk for breast cancer. Another strategy is to remove “at risk” tissue such as breasts and ovaries to help prevent breast and ovarian cancer. Drugs and surgical removal, it should be noted, are applicable only to a few inherited cancer syndromes.
Other things to consider include who will pay for the genetic test. Not all insurance companies pay for testing, although this is more likely if a genetic professional guides you through the process. If your doctor orders a test, the results will become a part of your medical record and will be known by future employers and health care providers.
The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination based on genetic information by employers and health insurance companies. However, this law does not apply to disability insurance, life insurance, or long-term care insurance. An earlier law, the Health Information Portability and Accountability Act of 1996, requires health care providers to protect patient privacy and sets some limits on the release of health records.
Direct-to-consumer or DTC genetic testing is offered by some companies. People collect their own tissue sample and mail it into a laboratory. This can be done without a doctor’s order in many states, but some states prohibit DTC testing.
Without guidance from a genetic counselor, people may misinterpret test results. They may experience a false reassurance or an unnecessary anxiety about results, and possibly make important medical decisions based on incomplete or misunderstood information. The Federal Trade Commission, which investigates complaints of misleading health claims, offers consumers a fact sheet for people considering a DTC test for cancer risk. The American Society of Human Genetics, a group of genetics professionals, recommends transparency in testing and regulations to assure laboratory quality.
Chen S, et al, “Meta-Analysis of BRCA1 and BRCA2 Penetrance,” J Clin Oncol 2007 April 10; 25(11):1329-1333.
“Costs of Genetic Testing,” www.genetichealth.com
“Genetic Testing for Hereditary Cancer Syndromes,” National Cancer Institute fact sheet, reviewed 4/11/2013
Hermsen BBJ, et al, “No efficacy of annual gynaecological screening in BRCA1/2 mutation carriers; an observational follow-up study,” British Journal of Cancer, Advance publication 10 April 2007.
Mayo Clinic Staff, “Genetic testing for breast cancer: Psychological and social impact Jan 18 2011. www.mayoclinic.com
Zagorski, Nick, “Genetic Testing for Cancer: Pros and Cons,” National Cancer Institute Benchmarks February 23, 2005
“Which Women Might Benefit From Drugs to Prevent Breast Cancer? New research suggests it depends on certain gene variations,” US News and World Report, June 13, 2013