There are many advances in genetic testing in the oncology setting pertaining to both germline DNA and tumor-based testing. It is important to understand the difference because there is a trend in some patients to use this testing together.
Germline DNA Testing
Germline DNA testing will assess DNA that you inherited from your mother’s egg and your father’s sperm. A germline mutation is a gene change that occurred in a reproductive cell (egg or sperm) that becomes incorporated into the DNA of every cell in the body of the offspring. When a mutation is found in germline DNA, it can be passed to offspring as well, so germline mutations are hereditary. Testing DNA from a blood sample or mouthwash “buccal” sample typically identifies Germline DNA mutations, but DNA could be sampled from nearly any tissue in the body.
Tumor DNA Testing
Tumor DNA testing looks at the DNA in cancer cells, typically evaluated after a biopsy or surgery. The DNA mutations seen in tumors most often come from spontaneous changes in the tumor over time, as it develops into a malignancy. As the cancer progresses, additional mutations are added as the cells grow out of control. These are called somatic alterations. Somatic alterations in DNA occur after conception. Somatic mutations can occur in any of the cells of the body except the germ cells (egg and sperm). Therefore, these are not passed on to children.
When a patient has tumor DNA testing, the goal is to improve patient care by detecting actionable genetic mutations (mutations that can be targeted therapeutically) with the goal of “personalized medicine.” Studies have shown that this can very effective for certain types of tumors. The crossover with germline mutations occurs when a clearly deleterious mutation seen on the tumor testing could also be a germline mutation (eg. one that is seen in the tumor because it was there in the cells from birth.) Somatic tumor testing may detect deleterious mutations in genes, such as BRCA1/2, that cause hereditary cancer risk. Germline DNA testing is not always run in parallel and it can be challenging for clinicians to identify which patients could benefit from further germline testing. Genetic Counselors are partnering with Oncologists to form teams with the goal of identifying these high-risk patients with inherited mutations.
Personalized Surveillance and Treatment
The overall trend is to personalize surveillance and treatment for patients based on their genetic profile and risk level. It is important for patients and their families to understand these types of testing and the impact on care.
We will continue to see more personalized management with advances in genetic technology. In fact, President Obama, announced an ambitious plan on January 30, 2015 to invest hundreds of millions of dollars in cutting-edge biomedical research for treatments tailored to the genetic makeup of individual patients, and said the effort would “lay the foundation for a new generation of lifesaving discoveries.” In recent years, targeted therapies have led to more effective treatments for various cancers and other diseases. The Food and Drug Administration has approved a growing number of specialized drugs for patients with specific genetic mutations, and the biotech industry has many more drugs in development.
National Cancer Institute at National Institutes of Health
Updated January 9, 2015
Washington Post. January 30, 2015