About Genetic Counseling and Testing
Cancer genetics is the study of cancer risk. At UC San Diego, we specialize in helping individuals understand their cancer risk and providing education about genetic testing, risk reduction, resources, and clinical trials.
Determining whether or not you have an increased risk of developing cancer can have potentially life-saving implications. For example, you may undergo more frequent screenings if you know you're at risk for a particular type of cancer or may elect to undergo preventive surgery. Finding out that you're not at increased risk can also be very helpful, especially when you have a family history of cancer. See Are You at Risk for Inherited Cancer?
It’s important to keep in mind that most cancer is not due to inherited mutations. Researchers estimate that only 5 to 15 percent of cancers are hereditary, depending on the type of cancer. A positive test for increased risk doesn’t indicate that cancer will develop.
Types of Inherited Cancer
Only these types of cancers have been linked to a gene alteration for which a blood test is possible:
- Early-onset prostate
- Endocrine cancers (e.g., thyroid, adrenal)
- Melanoma (skin cancer)
Genetic counseling and risk assessment is usually covered by most insurers. Your genetic counselor can discuss coverage based on your personal history and insurance plan, although it may be helpful to contact your insurance company in advance to determine coverage. In addition, there are financial assistance programs in place to help patients who cannot afford out of pocket costs for testing for hereditary cancer.
Preliminary screening generally includes:
- A thorough family history through multiple generations
- Reviewing medical records of family members (when possible)
- Evaluating the types of cancer in a family, as well as the ages at which family members were diagnosed
If the results indicate that you are a candidate for genetic testing, you may decide to have DNA testing to prove or disprove increased cancer risk. DNA testing can determine gene mutations that have been linked to increased cancer risk. There are two main types of genetic DNA testing:
- If you're the first person in your family to be tested: Ideally, the person in the family with the youngest age at cancer diagnosis is the best person to start with. Whole genes are scanned to see if a mutation (a change in the “normal” genetic sequence) can be identified. If a mutation is found, this confirms that the patient has a hereditary cancer syndrome and testing becomes possible for other family members. If a mutation is not found, then the risk of a hereditary cancer syndrome is greatly reduced, but might not be entirely eliminated depending on the unique family history of cancer.
- If there's a known genetic mutation in a family: Once a mutation has been found in a family, close relatives have a 50% chance of also having that mutation. Testing in this situation is very straightforward since the laboratory test gives a definitive result: the patient either does or doesn't have the mutation.
Obtaining test results and assessing risk are only part of the process. Each patient also works closely with a genetic counselor. We can recommend courses of action, such as lifestyle changes or more frequent cancer screenings. For high-risk individuals, we will also discuss preventive measures, like taking medications that can reduce cancer risk, having specialized screening, or undergoing preventive surgeries.
When appropriate, we may recommend other family members receive genetic testing and counseling. Choosing whether or not to receive these services is strictly up to the individuals affected.