Although most cancers are sporadic or occur by chance, a small percentage are due to inherited genetic (or germline) mutations, which can often be identified through genetic testing.
These mutations are different from mutations that spontaneously occur during one’s lifetime, called somatic mutations. Somatic mutations are discovered through genetic testing of a tumor sample.
Inherited mutations are present in every cell in the body and can be detected through genetic testing of any cell in the body, including cells that come from a saliva sample or a blood sample.
Who should get a genetic test?
People who should consider genetic testing include those with a strong personal or family history of cancer. Clues to a genetic predisposition for cancer include:
- Having a family member who was diagnosed with cancer at a younger age, such as before age 50 for some cancers;
- Having one family member with multiple cancers;
- Having a family member who develops rare or unusual forms of cancer;
- The presence of related cancers in a family over generations.
Testing is also recommended for people who have a known genetic mutation in their family for which they are at risk, such as a BRCA1/2 mutation that increases the risk of breast, ovarian, pancreatic and prostate cancer, or a mutation associated with Lynch syndrome.
“Depending on family and personal history, we can test for genes that confer an increased risk for developing cancer,” says Huma Q. Rana, MD, clinical director for Dana-Farber’s Center for Cancer Genetics and Prevention. “We can then assess a patient’s cancer risk based upon the results and form a plan to monitor for cancer or reduce the risk of developing cancer.”
Not everyone needs or benefits from genetic testing. “Genetic susceptibility to cancer is not that common within the total population,” says Rana.
Note that if you are diagnosed with cancer, your Dana-Farber care team will test a tumor sample for somatic mutations and germline mutations to help them select the best treatment for you.
What does a germline genetic test entail?
People undergoing testing meet with a genetic counselor and sometimes a physician to review their family history (see below) and provide consent. Testing is performed on a blood or saliva sample which is sent to a lab that specializes in genetics.
The results are returned to the physician and/or genetic counselor, who will discuss them with you. In some cases, there are actions you can take if you have results that indicate an elevated risk of cancer. Your physician or genetic counselor can help you understand your options and find appropriate follow-up care if that is what you choose.
Who qualifies as a genetic counselor?
Genetic counselors have master’s degrees in genetic counseling and are licensed professionals who help educate patients about inherited cancer syndromes and help interpret confusing or uncertain genetic test results. The counselors also help individuals gather family history, discuss options for risk management and family planning, and provide or refer individuals for psychosocial support as needed.
Find a genetic counselor at Dana-Farber.
What steps do you have to take before getting a genetic test?
Before getting a genetic test at Dana-Farber, you will meet with a genetic counselor who will help determine the likelihood of an underlying cancer predisposition. You should bring information regarding your and your immediate family’s specific cancer(s), age(s) at diagnosis, or information about pre-cancerous conditions such as colon polyps with you. If you have information about personal or family genetic test results, that information will also be helpful to share.
At Dana-Farber, some patients with certain cancer types may have a more expedited testing process where they watch an educational video and meet with our genetic testing coordinators, who are administrative personnel. This process aims to meet the increased demands for timely genetic testing.
Not every family is comfortable sharing information about cancer. However, information about cancer within a family can be valuable and help other family members and their health providers make better, more informed decisions about prevention and treatment. Information shared with a genetic counselor is protected by privacy laws in the U.S.
Dana-Farber researchers have also developed an online tool for people to use to determine if they have an elevated risk of certain cancers:
AssessYourRisk can help you learn more about your personal risk of breast and ovarian cancer.
At-home genetic tests are also available but come with caveats and considerations.
What does a positive genetic test mean?
A positive genetic test does not equal a cancer diagnosis. Rather, it means that your chances of developing it are higher than that of the average person. If you have a mutation that can cause cancer, you will work with a genetic counselor and physician to create a management plan. This plan informs you of what could happen and helps outline screenings or other options to prevent cancer from developing.
What research is happening for people with inherited cancer risks?
Many centers, programs, and research studies at Dana-Farber focus on people with genetic risks of cancer.
Learn more about syndromes, genes and programs at Dana-Farber. Those include:
- Breast and Ovarian Cancer Genetics and Prevention
- Center for BRCA and Related Genes
- Gastrointestinal Cancer Genetics and Prevention
- Lynch Syndrome Center
- Li-Fraumeni Syndrome and TP53 Center
Learn more about the many ongoing cancer genetics and prevention research studies at Dana-Farber.
About the Medical Reviewer
Dr. Rana received her MD from the Robert Wood Johnson Medical School at the University of Medicine and Dentistry of New Jersey in 2007. She completed her residency in internal medicine and her fellowship in genetics and genomic sciences at the Mount Sinai School of Medicine. She received her MPH from Harvard T.H. Chan School of Public Health in 2020. Dr. Rana joined the Dana-Farber Cancer Institute in 2012.