How can genetic testing help early detection, risk reduction, and prevention of cancer?

February 11, 2021
DNA Graphic

While most cancers do not have a strong connection to hereditary risk, an important piece of cancer prevention for some is genetic counseling and testing. We spoke to two genetic counselors at Dana-Farber Cancer Institute, Fatima Amir, MS, LGC, and Dillon Davis, MMSc, LGC, to learn more about being a genetic counselor, access to genetic counseling, and the role of genetics in prevention, risk reduction, and early detection.

What is genetic testing?

Genetic testing involves testing for “germline mutations,” mutations in the normal cells that a person is born with, which may increase the likelihood of developing certain cancers. This may include testing for mutations in genes like BRCA1 and BRCA2, which increases a person’s lifetime risk of developing breast, ovarian, pancreatic, and prostate cancers, or mutations in one of the five genes that may cause Lynch syndrome, which increases the risk of colorectal, endometrial, and other cancers. These mutations are different from “somatic mutations,” which exist in cancer cells and are not inherited but are acquired over one’s lifetime. Oncologists at Dana-Farber analyze patients’ tumors for somatic mutations through Profile, a large database of genomic data, which helps to match patients to the best treatments based on their tumors’ unique mutations.

For genetic testing of normal cells, a patient—who may or may not have cancer—meets with a genetic counselor, like Amir or Davis, for a consultation to discuss the option of genetic testing, which is typically done through a blood or saliva sample. Genetic testing is generally recommended for people with a strong personal and/or family history of cancer, to see if they carry certain mutations that increase their risk of developing cancer and, if applicable, may inform how their cancer is treated.

In recent years, more people have been conducting at-home genetic tests, most of which are not clinical-grade or definitive, but may test for some mutations, such as in the BRCA1 and BRCA2 genes, giving individuals increased access to genetic information. However, Amir cautions that these tests may not be comprehensive in assessing hereditary cancer risk and may give some consumers a false reassurance of being “off the hook” for hereditary cancer risk if they test negative. “On the other hand,” she adds, “sometimes consumers get unexpected information about their cancer risk from the results of these tests, which can be scary, so meeting with a genetic counselor can be helpful to clarify the meaning of the results and to determine the next steps.”

“We’re not just giving patients potentially scary information and saying they are definitely going to develop cancer,” Davis continues. “For most of these genes, having a mutation does not imply a 100% risk of cancer; it’s an increased lifetime risk over the general population. The level of increase in risk varies by gene and cancer type. Knowing about these risks can often help determine what steps patients can take for enhanced cancer screening and prevention.”

For the BRCA1 and BRCA2 genes, for example, which significantly increase the risk for breast and ovarian cancers, among others, someone may be recommended to do higher risk screenings for these diseases moving forward and to share this news with their family members, who may want to undergo genetic testing themselves to assess their risk. They may also be recommended for risk-reducing surgery to remove their ovaries and fallopian tubes after a certain age, as there is not currently reliable screening for ovarian cancer. These decisions can be difficult mentally and emotionally, which is where a genetic counselor and other members of the oncology team, including clinical psychologists, can help.

What does a genetic counselor do?

Dana-Farber’s Cancer Genetics and Prevention team consists of a variety of physicians, nurses, genetic counselors, program managers, and others who care for both adult and pediatric patients. Patients are referred to licensed genetic counselors by their oncologist, gynecologist, or primary care doctor, but sometimes set up appointments themselves, often if they are concerned about their family history of cancer.

“As genetic counselors, we collect family history and explain what genetic testing is, and what it means for patients and their families,” says Davis.

“I like to think of us as being at the intersection of health care, education, and counseling,” Amir adds. “The hope is that genetic counseling is made available and accessible to everyone who has a concerning personal or family history, so they may have a personalized understanding of their hereditary cancer risk.”

For patients who have mutations, such as in BRCA1/2, or hereditary conditions revealed through genetic testing, such as Lynch syndrome or Li-Fraumeni syndrome, they may enter specialized programs under the care of a genetic counselor and physician, to reduce risk and prevent disease, or to diagnose it as early as possible. These include Dana-Farber’s Lynch Syndrome Center, the largest and most comprehensive multidisciplinary cancer genetics group of its kind in the region, and the Institute’s Li-Fraumeni Syndrome and TP53 Center, the first comprehensive multi-disciplinary center in the world focused on personalized cancer risk management plans for children and adults with Li-Fraumeni syndrome, an inherited condition that causes an increased risk of a variety of rare cancers and of developing more common cancers at younger ages. 

Who most often receives genetic counseling?

Historically, genetic counseling has been most available to patients of Caucasian descent and for patients from a higher socio-economic background, but in recent years, there have been efforts by Dana-Farber and others to make it more accessible and equitable for all patients. Genetic testing is generally recommended for patients with a strong family history of disease, such as having diagnoses at young ages, having multiple diagnoses in an individual, having the same or related cancers in a family, or having a known genetic mutation in the family.

Amir has previously worked with the Whittier Street Health Center in Boston, as part of Dana-Farber’s Cancer Care Equity Program, to run a genetics clinic for a medically underserved community who may have personal or family histories of cancer. Four times a year, a genetic counselor visits the center to provide genetic counseling services and help build trust within the community, alongside a nurse navigator and geneticist. Amir has also partnered with Dana-Farber’s Community Benefits team to lead a workshop for community advocates for medically underserved populations on who may benefit from genetic counseling and when to be concerned about hereditary cancer risk.

“Across all of health care, we see racial disparities, and genetics is no different, unfortunately,” Amir says. “A lot of the research in genetics has primarily happened in individuals with Caucasian backgrounds, which affects who predominantly benefits from what we learn in genetics. There are studies being done now to try to diversify our genetics databases; however, there is much work that needs to be done.”

“We often can’t give as good answers to patients of color about what certain variants in their DNA may mean, because the data might not be available due to fewer studies among that population,” Davis adds. Research is being done at Dana-Farber and elsewhere to unveil more of this information and ensure at-risk communities have access to reliable genetic counseling.

Having a greater understanding of genetic risks in certain communities can allow for better informed preventative care. For example, understanding that individuals of Ashkenazi Jewish ancestry are more likely to carry a mutation in the BRCA1/2 genes allows genetic counselors to widely offer testing to those of Ashkenazi Jewish ancestry with a personal or family history of breast cancer, regardless of their age of diagnosis.

While the road ahead is long, there are efforts in the field to make genetic services more accessible to all populations, including here at Dana-Farber, with the goal of ultimately providing equitable preventative care to all communities.

This post is part of a series for Cancer Prevention Month, February 2021. With your generous support, the Jimmy Fund and Dana-Farber Cancer Institute are working to stop cancer before it starts, by improving prevention and detection for adults and children in Boston and around the world. You can support this lifesaving work by making a donation today.