By: Aniket Saha, MD, FAAP
Childhood cancer is rare. It's diagnosed in around 150 children per million around the world. In the United States, the majority of children with cancer are cured. Around 80% end up becoming long-term survivors.
While these statistics are encouraging, it's scary when your child gets a cancer diagnosis. You'll probably have plenty of questions. You may wonder if you passed on a genetic mutation to your child. Or maybe you're concerned about the risk of cancer in your other children or relatives.
Here are answers to common questions about the role of genes in childhood cancer.
If my child has cancer, what is the risk of their siblings or relatives developing cancer?
That depends on several factors:
- Does your child have what's called a
cancer predisposition syndrome?
These syndromes are caused by inherited gene mutations that increase the risk of developing cancer. Below is a list of some of the types:
Familial Wilms tumors
DNA repair disorders
Familial adenomatous polyposis syndrome
Other inherited colon cancer syndromes such as ataxia-telangiectasia
Less than 10% of childhood cancers are known to be related to these predisposition syndromes.
What type of cancer has your child has been diagnosed with?
Certain cancers are known to have a higher risk of an inherited genetic mutation. These include:
For example, an estimated 50–80% of patients with ACC, a rare childhood cancer, have inherited a genetic mutation. But less than 5% of childhood leukemias, the most common childhood cancers, have a hereditary component.
- Does your child's cancer have an acquired genetic mutation?
A test of your child's cancer may show an acquired mutation in the cancer cells. This is also known as a somatic mutation. This type of mutation isn't passed down from parent to child. It develops on its own. In fact, most cancers develop this way.
If testing shows that your child has a somatic mutation, you may be worried that the rest of your child's normal (non-cancerous) cells have the mutation too. Thankfully, this isn't the case for most kids.
In a tiny percentage of patients, a somatic mutation may be in the child's whole body. This is called a germline mutation. Childhood cancer researchers are still trying to figure out how often germline mutations happen. They are also looking into how these mutations affect kids. These researchers are learning new information every day.
Your child's oncologist can answer your questions about somatic and germline mutations once the testing is complete.
My child's cancer isn't because of any known genetic reason. Is the risk of cancer still higher in their siblings or relatives?
This is an important question. Unfortunately, the answer isn't entirely clear. Some significant studies have shown that there may be an increased risk of certain cancers in close relatives of children with cancer.
One study looked at the risk of cancer in first degree relatives (parents and siblings) of over 13,000 childhood cancer survivors in North America. This study showed that the risk of cancer was increased in siblings of childhood cancer survivors. This risk was not necessarily related to a known inherited cancer predisposition syndrome (see above). Studies done with large numbers of childhood cancer survivors in Australia and the United Kingdom also found similar results.
It's important to note that the cancers in the child's relatives were not always the same. They also didn't necessarily happen during childhood.
Experts don't fully understand why the risk may be increased for siblings. It's likely due to multiple factors like environment. There may also be genetic causes that scientists haven't discovered yet.
If there is a family history of cancer in my family, what is the risk of cancer in my child?
As mentioned earlier, most cancers don't have an inherited genetic reason. But if your family history concerns you, consider these questions:
Is there a strong family history of a similar or related cancer (such as breast and ovarian) in multiple family members?
Has this cancer occurred in multiple generations?
Is there a family history of multiple cancers in some family members?
Did some or all of these cancers happen to younger family members? For example, is there a family history of breast, ovarian, uterine, or colon cancer at an early age?
Is there a family history of unusual or rare cancers?
Using this information, you can talk to your pediatrician about your child's cancer risk. You can also ask about genetic testing and a referral to a genetic specialist or oncologist.
What should I do if know that my family has an inherited genetic predisposition syndrome?
Finding out that there is a family history of a cancer predisposition syndrome can be distressing. Certain syndromes may be suspected based on a physical exam. But they need to be confirmed with genetic testing.
Some syndromes may not have any obvious physical signs. Your child would need genetic testing for these too. However, if the inherited genetic predisposition is for an adult onset cancer, testing in a child is not recommended. Be sure to talk to your child's pediatrician before you have any testing done.
My child has a cancer predisposition syndrome. What should I do?
If your child has such a syndrome, it's understandable that you're worried. Keep in mind that being diagnosed with a cancer predisposition syndrome doesn't mean that your child will definitely get cancer. It means that the risk of your child developing certain cancers is higher compared to the general population.
Your child's risk depends on the type of syndrome they have and the cancers that are related to it. The risk also depends on your child's age, sex, and environmental factors.
For certain syndromes, cancer screening guidelines can be used to help detect the cancers that are related to the syndrome. Your pediatrician, a pediatric oncologist, and a genetic specialist can help guide you through all this.
Remember, less than 10% of cancers have a genetic basis. Most cancers, including childhood cancers, are random. They don't have any cause that can be identified. This is why there is so much ongoing cancer research. Scientists hope to understand better how and why people develop cancer.
Your child's pediatrician, oncologist, and genetic specialist can address your concerns. Don't be afraid to ask questions. Your child's health is important to everyone on your healthcare team too.
About Dr. Saha
Aniket Saha, MD, MS, FAAP is the Medical Director of the Division of Pediatric Hematology Oncology at Prisma Health Children's Hospital in Greenville, SC, and a Clinical Associate Professor of Pediatrics at the University of South Carolina Greenville School of Medicine. He serves on the Adolescent and Young Adult Oncology (AYA) Steering Committee at the Children's Oncology Group where he co-leads the AYA Responsible Investigator Network. Within the American Academy of Pediatrics, he is a member of the Section on Hematology and Oncology Education Subcommittee.