Genetic testing is a process that looks for alterations in genes, either in normal tissue or cancerous tissue. Alterations in normal tissue may identify patients who would benefit from cancer screening, and may inform individually tailored treatment. Alterations, or mutations, in tumor tissue may provide clues to the cancer’s behavior and help physicians design a treatment program with the greatest chance of success.
Germline testing involves looking for inherited genetic abnormalities that increase an individual’s risk of developing certain types of cancers or additional medical complications to allow individualized medical care. Tumor testing, which is a type of “somatic” testing, by contrast, involves probing tumor tissue for mutations or other abnormalities in cancer cell DNA that may or may not have been inherited.
Germline testing can indicate whether an individual has a heightened risk for developing certain types of cancers and can inform medical treatment. Somatic testing may reveal some of the mutations that are driving the growth of the cancer and may be targeted by advanced therapies.
Germline testing involves sending a blood sample (or sometimes other types of samples such as saliva or a small skin sample) to a specialized lab for analysis. Somatic testing involves removing a small amount of tumor tissue and sending it to the lab for analysis.
For germline testing, clinicians including physicians and genetic counselors will help parents interpret the results. The clinical team can explain the degree to which mutations increase a child’s risk for certain cancers, as well as measures that may lower that risk and steps to detect cancer at the earliest possible stage, when it is easiest to treat.
For somatic testing, your child’s physician will explain what the results mean. The mutations uncovered by somatic testing may indicate how aggressive the cancer is likely to be and which therapies are most likely to be effective against it. The physician may also prescribe drugs that specifically target the mutations thought to be driving the cancer’s growth. By doing tumor testing during the course of treatment, doctors may be able to detect new mutations that cause the cancer to become resistant to the drugs originally used to treat it. In such cases, other drugs may be available that target the new mutations.
The results of germline testing will be available to the genetic counselor and your child’s physicians. Somatic testing results will be available to the physicians only.
Genetic testing revealed that Hunter had the same genetic mutation found in his sister Amy.