If your child could be at risk for cancer, the sooner you discover that risk, the more you can do to prevent cancer or catch it in an early stage. Not every child needs to be tested, so it’s important to learn what genetic testing is and whether it’s the right decision for you and your child.
What is germline and tumor testing? What types of risk do they screen for?
To understand germline and tumor testing, it’s important to first understand how genes and cancer work. Genes are made of DNA sequences that code for a protein. A gene, or a combination of genes, plays a role in determining traits and conditions. A genome is the complete set of genes in an organism. Cancer always results from a genetic mutation, but that doesn’t mean every cancer is inherited.
Genetic testing looks at individual genes or a group of genes whereas genomic testing looks at a larger portion of a person’s genes. As it relates to cancer, there are two types of testing: germline and tumor (somatic) testing.
Germline testing looks for heritable genetic abnormalities that can affect a person’s risk for developing cancer. This type of abnormality presents as a mutation in every cell in the body. Tumor testing takes tissue from a tumor area to look for abnormalities in cancer cell DNA.
Germline testing helps to understand a person’s risk of developing cancer, and tumor testing finds abnormalities that may or may not be hereditary. Because germline testing reveals hereditary risk, it is helpful for other family members as well. Tumor testing is most often helpful for determining a treatment course for a patient who has already been diagnosed with cancer.
How do I know if my child needs to be tested?
If you or your doctor believe your child might have a hereditary form of cancer or be at increased risk for developing cancer or secondary cancers/tumors—or if you are considering having children and want to better understand possible risk for your children—you may wish to get genetic testing.
At Dana-Farber/Boston Children’s Cancer and Blood Disorders Center, genetic counseling is recommended for children who have:
- A diagnosis or prior treatment for a rare childhood cancer or brain tumor
- A diagnosis or prior treatment for a cancer of any type plus a strong family history of cancer
- An unusually young age of onset of a cancer or tumor, synchronous tumors, certain cancer or tumor types known to be related to hereditary risk, multiple afflicted family members, and others
- A parent (or another relative) known to have a cancer syndrome or a cancer gene mutation
Some genetic risk programs, including the one at Dana-Farber/Boston Children’s, offer genetic counseling to all pediatric oncology patients, or to anyone who wishes to better understand their genetic risk or hereditary cancer predisposition. Other programs may offer counseling to a more limited group of patients, so be sure to check your program’s specific requirements and recommendations.
Meeting with a genetic counselor doesn’t mean you have to go through with genetic testing. Your first appointment is just a chance to learn what your options are. If you decide to move forward with genetic testing, you should understand that it can take an emotional toll on people who may discover that they are at risk for conditions that they did not expect. This will be discussed with you in depth during your visit.
The field of genetics is rapidly changing. Genetic risk assessment will continue to become more effective, screen for more conditions, and become more widely available.