A lot has changed in genetic testing for breast cancer since the BRCA1 and BRCA2 gene mutations were discovered 20 years ago. In addition to advanced technology and tools to better find hereditary cancers, what cost thousands of dollars even a few years ago now costs much less, making genetic testing available to more people.
In the past two decades, “cancer genetic testing has changed in two main ways,” said Meagan Farmer, director of cancer genetic counseling at University of Alabama at Birmingham. “First, we know of many more genes associated with cancer predisposition than we did 20 years ago. Second, we can now analyze many of these genes at one time, relatively quickly and at increasingly affordable costs. Next-generation sequencing is the testing technology that allows us to do this.”
About 10 to 15 percent of most cancers are due to inherited genetic mutations. When these genes are present they greatly increase your risk of developing cancer, said Othman Laraki, president and co-founder of Color Genomics, which offers $249 at-home cancer gene tests that detect breast, ovarian and other common hereditary cancers. Provide a saliva sample, activate your account online, mail the kit in, and Color Genomics analyzes your genetic makeup, which is reviewed by a medical professional. A session with a board-certified genetic counselor is included.
What it is
“Next-generation sequencing refers to a technology that can sequence several genes at a very fast pace,” said Dr. Mary B. Daly, chairwoman of the department of clinical genetics at Fox Chase Cancer Center, Philadelphia. “The biggest change, however, is the creation of panels that can look for variants in multiple genes all at the same time rather than single-gene testing. As a result, we are discovering many more genes associated with different types of cancer.”
Before next-generation sequencing, patients who were suspected of having a hereditary reason for breast or ovarian cancer may have been offered analysis of the BRCA1 and BRCA2 genes, still believed to be associated with more than half of hereditary breast and ovarian cancer cases, Farmer said. Now, patients suspected to have a hereditary cause for their personal or family history of breast or ovarian cancer can be offered an analysis of 20 genes, and the same applies to genetic testing for predisposition to many other cancer types, Farmer said.
As test kits become cheaper and more available, experts caution that not all women need to be tested.
“Candidates for next-generation sequencing are individuals with family histories suspicious for cancer syndromes, individuals whose family history suggests the possibility of more than one cancer syndrome and individuals with cancer at an age earlier than expected,” Daly said.
“Red flags include early-onset cancer such as breast or colon cancer before age 50, rare types of cancer such as ovarian cancer, or multiple cases of the same or related cancers on one side of the family in multiple generations,” Farmer said.
Is it for you?
“People should know that it is important to meet with a genetic counselor or other genetic specialist before undergoing testing to help sort through all of the possible gene panels available to choose the one that best matches their personal and family history,” Daly said.
“We are most likely to find a hereditary cause for cancer in a family if testing is performed in someone that has had cancer. Testing of several genes through next-generation sequencing is most appropriate for someone that has had thorough pre-test counseling by a cancer genetics expert and is comfortable with the potential ambiguities related to many of the newer genes that can be tested,” Farmer said.
The science is always improving.
“These tests are good, but no genetic test is perfect. A negative test result does not rule out a hereditary contribution to someone’s personal/family history of cancer. If this history is suspicious, it may be appropriate for a person to undergo earlier or additional screening for the types of cancers seen in his/her family, even after a negative test result,” Farmer said.