Healthcare providers know how important it is to identify patients at risk for hereditary cancer. But, although such knowledge is clinically beneficial, it can be shocking, even devastating, to a patient. As genomic profiling in tumors becomes more widespread based on its utility in determining appropriate therapy, we will see an increasing number of patients with a potential germline mutation identified through this process.
To better understand the issue, it may be helpful to review the difference between a germline mutation versus somatic mutation.
- Somatic mutations (or acquired mutations) are found in tumors themselves and are the most common cause of cancer. These mutations occur from damage to genes in an individual cell during a person’s life, for instance, from tobacco use, ultraviolet radiation, and aging. These mutations are not hereditary. Genomic profiling, a.k.a tumor testing, looks for these abnormalities in a patient’s tumor and can help determine the best course of treatment for it.
- A germline mutation, in contrast, is hereditary and present from the time of conception in each cell. These inherited mutations account 5% to 10% of all cancers. Testing for germline mutations, usually performed on blood or saliva, will identify inherited mutations in genes, such as those in the BRCA1/2 genes, and may be performed in people with or without cancer.
Germline Mutation vs Somatic Mutation: Keeping a focus on the patient
Tumor testing is a priority because when a person has cancer, it is important to quickly determine which therapy will work best. But what if the family has a history of cancer, or the tumor seems unusual in a way, possibly suggesting it developed because the person was predisposed to this type of cancer? What then?
The next step in those cases is typically genetic counseling about a germline test.
As considered best practice by many medical associations, genetic counseling happens before a germline test so the most appropriate test can be offered based on the personal and family history, and the patient is prepared for the ramifications of the result for themselves and their relatives.
It’s important that patients really understand the implications of what it means to consent to a germline test. They often don’t realize they could learn that their children and grandchildren could have a significantly higher risk of developing cancer. They may not know that the test could potentially reveal they themselves are at risk for a totally different cancer in the future than the one initially diagnosed.
In short, pre-test genetic counseling provides the education that leads to truly informed consent.
When it comes to understanding a germline mutation vs somatic mutation, many patients don’t receive pre-test counseling. In fact, some labs conduct the somatic and germline test at the same time. It’s unclear how often the patient really understands that they are getting both types of tests. The test results could be quite a shock for someone coming in to discuss the best treatment approach to breast cancer, to then end up discovering they have a genetic predisposition to ovarian and other cancers and their family members are also at risk.
That’s where post-test counseling comes in. The genetic counselor discusses the results with the patient, including the medical, family, and psychological implications, along with helping individuals contemplate the next steps in their cancer treatment and prevention journey.
“Margaret” is a real person who came to us for post-test counseling (we’ve changed her identifying information in order to share her example). Her story provides more insights into the difference between a germline mutation vs somatic mutation.
Margaret was 63 when she was diagnosed with invasive breast cancer. Her oncologist ordered tumor testing; the lab performed a germline test along with the somatic/tumor test meant to provide information about the best treatment. It also revealed she had a BRCA2 mutation present from birth.
Margaret’s oncologist, realizing she didn’t have the expertise in genetics needed to explain the situation, referred her to us. Margaret arrived at the appointment thinking it was just a standard part of the testing process.
She was unnerved to hear the full test results, especially since she didn’t have a strong family history of breast or ovarian cancer. So suddenly, instead of just focusing on her breast cancer treatment, she had to think about her risk for her other breast, ovaries, and other cancer types – as well as her adult son and daughter’s potential risk for breast, ovarian, male breast, prostate, and other cancers.
By the end of the counseling session, she was glad she had the information, and she was able to talk with her family about their risk and their need for genetic counseling and testing. After her experience, Margaret was able to provide some explanation on a germline mutation vs somatic mutation with her loved ones.
Germline Mutation vs Somatic Mutation: Barriers to care
Patients frequently don’t receive the genetic counseling they need. It’s understandable: A healthcare provider may want to get a patient into treatment as quickly as possible, and they think that referring the patient to a counselor will slow the process (it doesn’t have to since very expedited appointments by telephone are easily available).
Lack of access to genetic counselors is a misconception. Many regions lack genetic counseling offices nearby, but today, genetic counselors are available anywhere in the country via phone and video. This is a great resource to better understand a germline mutation vs somatic mutation.
Finally, as a healthcare provider, it’s easy to assume patients and families understand more about genetics than they really do. In fact, patients themselves may assume they understand what’s involved. Most, however, need someone to help unpack the implications for them, not only for positive test results but negative ones as well. For instance, if a woman tests negatively for a BRCA mutation, she may erroneously think that she’s no longer at risk for breast cancer. In these instances, most patients will not know the difference between a germline mutation vs somatic mutation.
A key member of the care team
As part of a multidisciplinary care team, a genetic counselor will have the same sense of urgency about treatment. They will also ensure the patient is fully informed of all the genetic implications of the testing. It’s not a burden that healthcare providers need to carry. Just as providers call in other specialists as needed, they can call on genetic counselors.
Genetic counselors, with training in medical genetics, molecular genetics, and psychology, are well equipped to explain complex genetic concepts in lay terms and answer questions about everything from genetic discrimination to how to mitigate disease risks. They also work with providers to ensure that they are armed with all of the genetic information needed to manage their patient’s care, like explaining the differences between a germline mutation vs a somatic mutation.
Referring to an outside specialist or expert is how every other aspect of medicine works. Now that it’s more evident how genetics impacts all areas of medical care, it’s becoming much more important to consult genetics specialists to ensure appropriate application of these new and expanding technologies and tests in everyday practice.
InformedDNA leverages the expertise of the largest, fully employed staff of lab-independent, board-certified genetics specialists in the U.S. to help ensure that health plans, health systems, hospitals, pharmaceutical companies, clinicians, and patients all have access to the highest quality genetics services.
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