Genetic Testing Can Lead to Precision Medicine Therapies for Cancer

Broad-based genetic testing could identify inherited genetic mutations and accelerate precision medicine therapies for patients with cancer, according to a study published in JAMA Oncology.

Hereditary factors play a key role in the development of many cancers, researchers at Mayo Clinic’s Center for Individualized Medicine noted. Identifying genetic predispositions for certain cancers can have significant implications for treatment decisions, interventions, cancer screenings, and genetic testing for patients and close relatives.

Selecting patients for genetic testing has traditionally been based on pathologic features of the cancer, age at diagnosis, family history of cancer, and other factors named in clinical guidelines. Few studies have examined the impact of broad-based testing for gene mutations in patients with cancer compared with more traditional methods of selection.

Over the course of two years, Mayo Clinic researchers provided free genetic testing and counseling for 3,084 patients as part of their standard cancer care. The project included a wide range of cancer stages and types, such as breast, colorectal, lung, ovarian, pancreatic, bladder, and prostate cancers.

The results showed that with standard guidelines, physicians were only able to find 48 percent of patients with an inherited genetic mutation.

"We found that 13.5 percent of patients had an inherited mutation in a gene associated with the development of their cancer," said Niloy Jewel Samadder, MD, a Mayo Clinic gastroenterologist and hepatologist, who is the study's author.

"More than half of the patients who developed cancer due to inherited mutations were being missed, and that has major implications for family members. Everyone has some risk of developing cancer, and in most cases the disease develops by chance. However, some people are genetically predisposed to developing certain types of cancer, such as breast or colon cancers.”

When researchers examined the effects of a genetic mutation discovery, the team found that one-third of patients with the highest-risk cancer genes had a change in their medical management, including the type of surgery or chemotherapy they received.

"This targeted treatment would have been lost if the patients had not received genetic testing," Samadder stated.

The results demonstrate the importance of genetic testing for all patients, and not just specific individuals.

"Genetic testing is underutilized in cancer care, both for patients and for their families, often due to outdated guidelines that restrict testing to a narrow group of high-risk patients," said Robert Nussbaum, MD, chief medical officer of Invitae Corporation.

"All cancer patients should have access to complete genetic information that can guide their care and inform their families' health."

Additionally, high-risk patients should share the heritable-cause of the disease with their relatives, which will allow family members to pursue disease care for earlier cancer management and detection.

"We can help prevent cancer in their loved ones because it is genetic, and they share these cancer-causing genetic changes with their children, siblings and others in their families," Samadder said. "We can target prevention strategies for those high-risk individuals and hopefully prevent cancer altogether in future generations of their family."

All blood-related family members of patients found to have a genetic mutation were offered free genetic testing. Overall, one in five of these family members underwent testing, the researchers said.

Going forward, the research team hopes to be able to incorporate the study’s results into the care of all patients with cancer at Mayo Clinic. The study demonstrates the potential for broad genetic testing to accelerate the development of precision medicine therapies for cancer.

"Steps are being taken to ensure all patients are offered genomic sequencing to better understand the genes that led to the development of their cancer, and how to precisely target treatment and improve survival," said Samadder.