Dana-Farber Cancer Institute

What to Expect From Genetic Testing

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    How Genes Work 

    • Think of genes as instructions written in a special code. These instructions are made of DNA, the building block of life found in almost every cell.
    • We inherit two copies of most genes, one from each parent. These act like a recipe for making proteins, which are essential molecules that do many jobs in our bodies.
    • The specific order of DNA letters in a gene is the code itself. Changes to this code, like typos in a recipe, can affect how the protein is built or even prevent it from being made at all. 

    What Is Genetic Testing?

    Genetic testing is a process that looks for mutations in a person's genes. Alterations in certain genes may lead to an increased risk of cancer. Therefore, genetic testing results may be helpful in tailoring cancer screening recommendations.

    Genetic testing involves sending a blood, saliva or skin biopsy sample to a specialized lab for analysis. Results are returned to the ordering physician and genetic counselor, who then discloses them to the patient and arranges appropriate follow-up care. 

    Are There Different Kinds of Genetic Testing?

    In this episode of Cancer Questions with Dana-Farber, Huma Rana, MD, MPH, physician at Dana-Farber Cancer Institute, highlights the different types of genetic testing for cancer: germline DNA testing, somatic sequencing and CT DNA testing.

    Do Cancers Always Have a Genetic Component?

    Huma Rana, MD, MPH, physician at Dana-Farber Cancer Institute, explains how 15% of cancers are linked to inherited mutations. These mutations frequently affect tumor suppressor genes, increasing the risk of cancer development in individuals born with such mutations.

    Preparing for Your Visit 

    A visit to the Cancer Genetics and Prevention Clinic may include time with a physician, a genetic testing coordinator, and/or a genetic counselor, all of whom have expertise in all forms of inherited cancer conditions. We educate patients about cancer risk and its implications for them and their family members. Working with referring physicians, we design individualized programs to monitor for the earliest signs of cancer — diagnosing if it occurs, and, in many cases, preventing it from arising.

    Information regarding personal and family cancer history — including the specific cancer(s), age(s) at diagnosis, information about pre-cancerous conditions such as colon polyps, and copies of personal or family genetic test results— are requested for your visit. Other medical records such as pathology reports, surgical reports, or summary notes are often useful.

    The Role of Genetic Counselors

    Genetic counselors are trained licensed professionals who have earned a master’s degree in genetic counseling from an accredited program. Cancer genetic counselors specifically counsel patients about inherited cancer syndromes, the chance they might carry a gene mutation that confers increased cancer risk, the mechanics of genetic testing, and the implications of being found to carry or not carry a genetic risk for cancer.

    The role of a genetic counselor is to assist individuals and families in understanding genetic disorders. Genetic counselors:

    • Gather a three-generation family history
    • Obtain informed consent for genetic testing when appropriate
    • Discuss options for risk management and family planning
    • Provide, or refer individuals for, psychosocial support as needed

    Genetic counselors will discuss common concerns about genetic testing, including issues of insurance discrimination and confidentiality. They will also review possible results, as well as the cost and logistics of testing, insurance coverage, or options if your insurance does not cover these services.

    Your genetic counselor will guide you in making the best decisions regarding testing for yourself. If a positive result or mutation is found, the genetic counselor will help you communicate this information with relevant family members and can help them arrange their own testing. Genetic counselors often help interpret confusing or uncertain test results, and they also educate patients and providers about new testing options. For this reason, genetic counselors may maintain contact with patients over time.

    Genetic Counseling for Cancer Risk: What to Expect

    Genetic counselor Kathy Schneider, MPH, LGC, describes what to expect from a genetic counseling visit, who should consider genetic counseling, and how it can be helpful in understanding risk for certain types of cancer based on personal and family history.

    The Role of Genetic Testing Coordinators

    The Genetic Testing Coordinator (GTC) team meets with cancer patients through the Rapid Access Cancer Genetic Testing process. This approximately 30-minute visit includes viewing an informative video about genetic testing. The GTCs go through testing and billing logistics and the informed consent form, and they can arrange testing the same day. Many patients will meet with a GTC as part of their first visit within our Center.

    Understanding Your Results

    In the videos below, Dana-Farber cancer genetics specialists provide answers to a variety of questions about interpreting test results. 

    What is a Variant of Uncertain Significance (VUS)?

    Genetic counselor Helen Dellas, CGC describes what a VUS diagnosis means, and how this may or may not relate to risk for certain types of cancer.

    What Are Germline and Somatic Mutations?

    Huma Rana, MD, Clinical Director of the Center for Cancer Genetics and Prevention describes the difference between germline and somatic mutations, and implications for cancer treatment.

    What is Mosaicism?

    Genetic counselor Kathy Schneider, MPH, LGC, describes mosaicism, and how genetic counselors assess the risk for cancer for individuals found to have mosaicism.

    Mosaicism vs. Circulating Tumor Cells

    Genetic counselor Kathy Schneider, MPH, LGC, describes the difference between mosaicism and circulating tumor cells.

    Genetic Testing and Insurance Coverage

    There are many factors that determine if your insurance will pay for your genetic testing, and several payment options. This can be discussed in more detail during your visit. See the FAQ below for more information: