Identifying Your Genetic Risk of Cancer

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Patients should consider genetic testing when cancer runs in the family.

Many cancers begin as a fluke mutation in a single cell. Yet in up to 10% of cancer cases, one or more mutations wind their way through family trees with a chance of affecting each new member. When mutations are deemed hereditary, also known as "germline," they are present in every cell, including egg and sperm, and can thus be passed on to subsequent generations.

Each person has 46 chromosomes — 23 from each parent — that contain 20,000 to 25,000 genes. These chromosome pairs allow for a backup, so a mutated gene’s healthy counterpart can code for the correct protein. For a hereditary cancer to develop, both copies of the gene must be affected, although it is also possible to develop such a cancer if one mutated gene is inherited and its backup develops a mutation later in life.

Inheriting a mutation doesn’t mean it’s certain that someone will develop cancer, but it does put that person at risk. Researchers have identified many inherited mutations that account for more than 50 hereditary cancer syndromes.

For instance, the lifetime risk of developing breast cancer or ovarian cancer is significantly increased for a woman if she inherits a BRCA mutation. In addition to breast cancer and ovarian cancer in women, BRCA mutations are associated — to a lesser degree — with an increased risk of fallopian tube cancer and peritoneal cancer in women, breast cancer and prostate cancer in men, and pancreatic cancer in both men and women.

For patients with breast cancer and ovarian cancer, early identification of a BRCA mutation will significantly help in creating a treatment plan. Patients who test positive for a BRCA mutation may respond to certain therapies better than those who do not have the mutation, and may be eligible for different clinical trials.

Inherited gene mutations can’t be repaired, but they can be found through genetic testing. Requiring little more than a simple blood draw or saliva sample, genetic testing is now available for dozens of hereditary cancer syndromes, which are caused by alterations in genes that suppress or activate tumor growth. But genetic testing should only be done within the framework of genetic counseling.

Genetic counselors help patients decide whether to undergo genetic testing and help them understand the results and provide context. Working with genetics professionals, patients and their families can explore the possible consequences of genetic testing and develop realistic expectations of what might or might not be learned in the process.

Patients might be candidates for genetic testing if they have one or more of the following:

  • Early-onset cancer (usually before age 50).
  • More than one cancer diagnosis.
  • A strong family history of cancer or the presence of rare cancers.

The details of what constitutes “early-onset” or “strong family history” vary according to the cancer type or specific genetic mutation. A pedigree is created based on family history of cancer to determine who will most likely benefit from genetic testing.

Testing can provide information that either confirms high-risk status or rules out the presence of a genetic alteration found in other family members. For those who test positive for certain genetic mutations, increased screening might be needed. Some patients might also consider chemoprevention strategies to help lower their risk of second cancers or recurrence. In other cases, cancer could be prevented with prophylactic procedures, such as surgery, or behaviors.

Because gene alterations often predispose individuals to many types of cancer, identifying genetic status early can aid in diagnosis and medical decision making. It can also alert relatives that they might benefit from genetic testing, cancer screening and prevention measures.

Not everyone suspected of having a genetic mutation should necessarily be tested, for example, if the results wouldn’t alter the patient’s medical course.

Patients considering genetic counseling should visit cancer.gov/cancertopics/genetics/directory to find a local genetic counselor.

Taking Charge of Your Own Genetic Testing? Take Some Precautions, Too.

People who suspect that they are predisposed to a certain inherited cancer, and who want to be tested to find out if they specific gene mutations, have a growing variety of genetic tests from which to choose.

Testing of a person's DNA is offered for many of the more common inherited syndromes that can cause cancer, including hereditary breast cancer and ovarian cancer syndrome, caused by mutations in the BRCA1 or BRCA2 genes. Others, each caused by specific gene mutations, include Li-Fraumeni syndrome; Cowden syndrome; Lynch syndrome; familial adenomatous polyposis; retinoblastoma; multiple endocrine neoplasia type 1 (Wermer syndrome); multiple endocrine neoplasia type 2; and Von Hippel-Lindau syndrome.

The tests for these mutations, many of which can look for multiple mutations associated with a specific disease, are often prescribed by a physician and require a small sample of body fluid or tissue, such as blood, saliva, cells from inside the cheek, skin cells or amniotic fluid. The tests are then sent to a lab and later returned to a doctor or genetic counselor, who can explain the results to patients.

However, there are tests out there that can be taken without a doctor’s prescription or guidance. These are called direct-to-consumer (DTC) genetic tests that are often marketed to people online. They can be purchased via the internet or at local drug stores and may require a cheek swab or saliva sample that people can send through the mail. Test results are then sent back via mail, online or over the phone. These tests look for mutations to the BRCA genes, to those linked to Lynch syndrome and to others associated with a few health issues not related to cancer.

While people are hoping to find answers about their genetic risks, they may not fully comprehend the results. This is a problem that the Food and Drug Administration and Centers for Disease Control and Prevention have pointed out with DTC genetic tests. Both agencies have stated that some of these tests lack scientific validity and should be taken in context only after a full medical evaluation.

The National Cancer Institute (NCI) advises seeing a genetic counselor, doctor or other health care professional trained in genetics to discuss results and what the next steps should be. These may include preventive care, screening, referral to support groups, the provision of emotional support and help with decisions about whether other family members need to be tested.

For those who do choose to go with a DTC genetic test, the NCI suggests using a laboratory that meets both state and federal testing guidelines. Currently, labs that perform genetic testing are subject to the federal Clinical Laboratory Improvement Amendments.

While their ease of access may make these tests appealing, they do not come without a price. The cheaper tests run about a couple of hundred dollars, and panels testing for multiple conditions or gene mutations can cost into the thousands. It’s important to note that, often, these costs are not covered by health insurance.

Before ordering a test, check the company's privacy policy, including its rules about giving data to police who request it.

Furthermore, there has been an uptick in unqualified "health advocates" promoting DTC genetic tests to consumers with promises of free testing to people who don't qualify for it, and who may use personal health care information to fraudulently bill insurance companies. To stay safe, start by asking questions of health professionals such as your primary care doctor, OB/GYN or oncologist, or checking the website of Facing Our Risk of Cancer Empowered at tinyurl.com/yxmfzjrw.