March 05, 2020
It is a truth universally acknowledged that cancer prevention and early cancer detection saves lives.
As scientists and physicians at the major cancer centers work together to unravel the link between genetic alterations and cancer risk, genetic testing is rapidly becoming an impactful tool for matching patients to individualized cancer screening programs.
Often called the “Angelina Jolie effect” — based on the actor's laudable effort to enhance understanding of increased cancer risk for patients with alterations in the BRCA1 or BRCA2 genes — the general public has become appropriately more aware of the importance that genetics can play in cancer risk.
Put most simply, genetic testing utilizes DNA usually obtained from small amounts of saliva or blood to identify a genetic mutation, or change, in your DNA that may increase your risk of developing certain cancers. This is determined by “sequencing” the DNA, which reads the specific DNA code for a subset of genes known to be important for affecting cancer development.
Individuals with a strong family history of cancer or those of a certain ancestry, such as Ashkenazi Jewish ancestry, might be more likely to carry these genetic mutations, but lack of a family cancer history does not mean that someone won’t be a carrier. In many cases, genetic risk of cancer arises spontaneously through DNA errors that occur in developing embryos. In other words, genetic risk can result from a spot of ill-timed bad luck, on or before your journey began at the single cell stage.
Being aware that you have a genetic mutation that might increase your risk of developing cancer can help you and your doctor work together and create a personalized plan to help increase your chance of prevention or early detection.
For a man carrying specific alterations in the BRCA2 gene, there may be concern for increased risk of prostate or pancreatic cancer development. The team approach is then taken. After meeting with a genetic counselor, a personalized plan for that patient may entail earlier or more frequent prostate cancer screening, and support for helping the patient change behaviors that may further enhance pancreatic cancer risk, like smoking.
At the Sidney Kimmel Cancer Center at Jefferson, the Men’s Genetic Risk centralizes these plans, and coordinates with the patient’s care team to tailor the individual health plan. Further discussions are also had with regard to “cascade” testing, or testing family members who may also be at risk. As such, genetic testing can impact not just the patient themselves, but family members as well.
Genetic testing might be recommended to someone if they have a strong family history of cancer, which may include several first-degree relatives — parents, siblings and children — with cancer; many relatives with the same type of cancer; relatives who were diagnosed at a younger-than-normal age; or a relative diagnosed with a rare cancer, such as a male with breast cancer.
Someone who has already been diagnosed with cancer may benefit from genetic testing as well, especially if they were diagnosed at a young age or have a family history of cancer. Cancers with a known hereditary component include breast, ovarian, uterine, prostate, colorectal, melanoma, pancreatic and stomach cancers.
Having a family history of cancer is not limited to a having a family history of the same cancer. For example, and related to our case above, a man whose mother or sister had breast cancer might be at risk himself for prostate cancer.
It is also important to note that the presence of a gene mutation is also relevant when treating existing cancer. Certain genetic mutations are also associated with a greater risk of having an aggressive cancer and resistance to certain therapies, which can help your doctor manage specific tumor types.
Your results may help your doctor decide on the best treatment regimen, because researchers have found that some treatments are more effective in people with certain gene mutations. In fact, the FDA has recently approved cancer therapies that are only for patients whose tumors have specific gene alterations and it is expected that many more such “targeted therapies” will be approved and ready for use in treating cancer.
So what if you have been tested and you do not have an identified genetic risk? It is important to note that not having a family history of cancer or genetic risk of cancer does not guarantee that you will never develop cancer. With regard to family history, the National Cancer Institute notes that only 5-10% of cancers are due to inherited gene mutations.
Additionally, having a family history of cancer does not mean that you are certain to be diagnosed with cancer one day yourself. Genetic testing can help inform you of your genetic risk for certain diseases, but it does not inform you of your overall risk. Other factors that contribute to an increased risk for cancer include environmental factors and lifestyle choices, many of which are modifiable.
If you are considering genetic testing or have questions about whether you or your family should undergo testing, talk to your doctor or other health care providers. Talking to a health professional or genetic counselor can help you decide whether you would benefit from testing. They will collect your family and personal health history, explain what kind of information the test can provide you, and help you decide whether the test is right for you.
After undergoing genetic testing, it is important that you talk to your health care provider about what the results mean for you, whether positive or negative. The results can be confusing, and they can help you interpret your results, allay any fears, discuss potential implications for your family, and help you make an informed decision about how to proceed based on the results. Discussion with a specialist is important for future care decisions.
If appropriate, your doctor may discuss cancer risk-reduction strategies with you, like preventive surgery, medications that help reduce risk or lifestyle changes. They also may recommend alternative screening options to help detect the cancer early, such as beginning mammograms before age 40 or having a colonoscopy at 45 rather than 50.
In addition to the clinical genetic testing, a growing number of companies are making tests available to consumers that can provide insight into one’s ancestry, as well as certain health information. There are a few things to keep in mind regarding these direct-to-consumer tests if you decide to go ahead with one.
Ancestry DNA tests are typically not clinical grade, meaning that the information is not of the established quality required to change someone’s health plan. Even if a cancer gene is suspected on these tests, confirmation would be required using a clinical-grade test that has been deemed valid and reliable for detecting cancer gene alterations.
In addition, many at-home tests are very small in scale, and leave out testing of many genes known to be influential in determining cancer risk. For example, an at-home test might screen for mutations in the BRCA1 and BRCA1 genes, but not for the genes associated with Lynch syndrome, an inherited disorder that increases the risk of several cancer types, including colorectal cancer.
There is a growing concern that negative results from an at-home test can provide consumers with a false sense of security. These tests should not be used as a substitute for the genetic counseling and testing you would receive from your health care provider, who will usually re-order a clinical test to confirm the results, and help you understand the results of the test.
A common concern for people considering genetic testing is discrimination based on their genetics. The Genetic Information Nondiscrimination Act is a federal law that protects individuals from genetic discrimination. GINA prohibits health insurers from discrimination based on the genetic information of enrollees, meaning they may not use genetic information to make decisions regarding eligibility, coverage, underwriting or premium-setting. However, GINA does not cover disability, life and long-term care insurance.
GINA also prevents employers who have at least 15 employees from using genetic information in employment decisions such as hiring, firing, promotions, pay and job assignments. Additionally, some states have enacted laws that offer additional protections against genetic discrimination. For more information on GINA and genetic discrimination, click here
In sum, cancer genetics is a rapidly evolving field, and the era is upon us wherein individual wellness plans will be as guided by genetic information as they are by vital signs. It was not long ago when the only genetic testing option was examining the BRCA1 and BRCA2 genes for inherited mutations associated with breast and ovarian cancers.
Fast-forwarding to 2020, we not only understand more about BRCA mutations, but we have discovered that there are many hundreds of other genes related to cancer development and progression. If you had BRCA testing many years ago or were told previously that you were ineligible for genetic testing, talk to your doctor.
As we learn more about genetic mutations and we continue to expand the recommendations for testing to include more people, your doctor might recommend that you undergo genetic testing now or consider additional genetic testing. Understanding your genetic code just might be a life saver!
Karen E. Knudsen, Ph.D., enterprise director at the Sidney Kimmel Cancer Center – Jefferson Health, oversees cancer care and cancer research at all SKCC sites in the Greater Philadelphia region. She writes occasionally on topics related to cancer.