The Test of Time: Genetic Testing For Hereditary Cancer Risk

Genetic counseling and testing for hereditary cancer risk have been integral to patient care for many years. The process gives patients information regarding their risk of developing certain types of cancer and guides recommendations for screening and prevention. Genetic testing can also offer patients information that can be shared with their family members to determine if they, too, are at increased risk of developing cancer.

Why Genetic Testing?

Since the 1990s, when this kind of testing became available, the ability to more broadly screen and interpret the results has evolved extensively. Patients who underwent testing many years ago may wonder if they should be tested again. In fact, one of today’s sophisticated tests may be in order, particularly for those who previously screened negative for cancer predisposition genes or whose testing looked at a limited number of genes.Risk factors for hereditary cancer include the following:

• Early-onset cancer, often prior to age 50.
• Multiple primary cancers.
• Ashkenazi Jewish ancestry with a personal and/or family history of breast, ovarian, prostate and/or pancreatic cancer.
• The same or related cancers in two or more close family members.

Genetic testing is typically most informative in a family if it begins with a relative who has a personal history of cancer that suggests hereditary risk. Because awareness of such cases is not always possible, genetic testing may still be warranted for an individual who has not had cancer but has a significant family history.

Who Should Consider Additional Genetic Testing?

Historically, genetic testing for cancer risk focused on only a few high-risk genes associated with specific types of cancer. More recent advances in technology allow patients to undergo genetic testing using what is known as multigene panel testing. This type of testing provides for analysis of many genes at once using a single blood or saliva sample. Because many different genes may cause the same or a related type of cancer, multigene panel testing can be an efficient option. This testing typically looks for mutations in genes with a high or moderate risk of contributing to the development of cancer. The testing may include genes associated with several types of cancer, which may be particularly useful for a patient with a more extensive personal and/or family history of the disease or those with limited information regarding their family’s cancer history.Some patients may have undergone genetic testing for hereditary breast and ovarian cancer that was limited to the high-risk genes known as BRCA1 and BRCA2, or they may have had testing for hereditary colon cancer that was limited to the genes associated with Lynch syndrome. If those prior results were negative, it is often reasonable for those individuals to consider more comprehensive testing using a multigene panel. Positive results could indicate a genetic mutation that is known to cause an increased risk of developing cancer, giving a patient and their family members updated information about risks and recommendations.

If the results from panel testing are negative — no mutation in any of the genes was identified — this finding should be interpreted in the context of a patient’s personal and family history of cancer, and increased cancer screening may still be recommended. Another possible result: a variant of uncertain significance, which means that a change in one or more of the genes evalu- ated was detected, but it is not clear whether that change raises the risk of cancer. The majority of uncertain variants will eventually be reclassified as benign because data about those genetic mutations, including informa- tion from individuals with those variants who were followed over time, will shed light on their meaning. If information about a mutation or variation of uncertain significance changes, genetic counselors can contact patients to update them on any steps that should be taken.

A patient who previously tested positive for a BRCA1 or BRCA2 mutation, for example, is less likely to now test positive for a mutation in another breast cancer gene that would significantly change their screening and/or prevention recommendations. However, it may still be worthwhile for that patient to discuss prior genetic test results and personal and family history with a genetic counselor to determine if updated testing via a multigene panel is warranted.

Can My Genetic Test Results Be Used Against Me?

It is important to understand that knowledge about the cancer risks and screening recommendations for many genes will continue to evolve and change. The results of multigene panel testing can be complex, with significant implications for patients and their family members. Therefore, it is recommended that all patients review their personal and family history with their physicians and ask for a referral to a genetic counselor to discuss prior results and the possible need for additional testing with a multigene panel.The Genetic Information Nondiscrimination Act of 2008 (GINA) prohibits employers and health insurers from using genetic information, including family history and genetic test results, to discriminate against patients. For certain groups of patients, other laws or policies may provide similar protections. However, GINA does not protect patients from discrimination by life, disability or long-term-care insurance companies. For more information, visit GINAHelp.org.

TIFFANI A. DEMARCO, M.S., CGC is a certified licensed genetic counselor and director of the cancer genetics program at Inova Schar Cancer Institute in Fairfax, Virginia.