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Genetic Testing and the Risk of Inherited Cancer

Did you know some types of cancer run in families?

“We know that even if you have genetic mutations that give you a high risk of cancer, environmental factors can modify that risk quite a bit,” says Xavier Llor, MD, PhD, Co-director of the Smilow Cancer Genetics and Prevention Program.

Cancer is caused by changes to genes that control the way our cells function, especially how they grow and divide. You can inherit these from your parents if the changes are present in germ cells, which are the reproductive cells of the body (eggs and sperm). These are called Germline mutations. When a germline mutation is inherited, it is present in all your body cells from birth.

Cancer-causing genetic changes can also be acquired during your lifetime, as the result of random errors that occur as cells divide or from exposure to cancer causing substances that damage DNA, such as certain chemicals in tobacco smoke, alcohol or prolonged exposure to ultraviolet rays from the sun. These changes that occur during your lifetime are called Somatic changes. Somatic mutations are not present in all cells of the body, are not inherited, and are not passed down to your children. Most human cancers are thought to be caused by acquired (somatic) mutations.

Germline genetic mutations play a major role in about 5 to 10 % of all cancers.

Research has discovered mutations in specific genes with more than 50 hereditary cancer syndromes, which are syndromes that may predispose individuals to developing certain cancers. If you have a family history of breast, ovarian, uterine, or colorectal cancer, you may have a higher risk for these cancers. For example, it is estimated that approximately 70% of women with a BRCA2 mutation will get breast cancer by age 80 while the other 30% won’t. Unfortunately, there’s no way to tell whether a woman with a BRCA2 mutation will or won’t get breast cancer, and since there is a higher chance of getting cancer than not, your oncologist will suggest standard of care treatment options. It is also important to know that even if a cancer-predisposing mutation is present in a family, not everyone who inherits the mutation will necessarily develop cancer.

Telling your doctor about your family health history is a first step to find out if you may have a higher cancer risk.

You can go through a handy checklist of syndromes to help you get a preliminary understanding of what kind of cancer risks you face before a consultation; this will help you organize your thoughts, ask the relevant questions and have a more focused conversation with your doctor. It will also help you and your doctor decide what tests you need, when to start, and how often you need to be tested. Knowing your family health history also helps you and your doctor decide if genetic counseling or testing may be right for you. Of course both are only useful if the test results are adequately interpreted (that is, they can clearly tell whether a specific genetic change is present or absent) and provide information that will help guide a person’s future medical care.

The most commonly inherited cancer risk mutations are:

  • Hereditary breast and ovarian cancer syndrome (HBOC) which refers to mutations in BRCA1 and BRCA2 genes, which increase the risk for breast, ovarian, pancreatic, prostate and other cancers.

  • Lynch syndrome which refers to mutations in certain genes (EPCAM, MLH1, MSH2, MSH6 and PMS2), which increase the risk for colorectal, endometrial and other cancers.

Based on your discussion, your physician can recommend further consultations with an oncologist or a genetic counselor.

There are a variety of factors that are taken into consideration for high-risk people including but not limited to age, comorbidities, the gene mutation in question, gender etc. Based on these factors, your physician may suggest the following options to manage your risk including:

  • Screening tests related to your genetic risk to find cancer in its early stages, when it is most treatable.

  • Medications or other treatment options to lower the risk for cancer.

  • Surgery to remove high-risk tissue before cancer can develop. This is called "prophylactic" or "risk-reducing" surgery.

Although you may be diagnosed with a cancer syndrome it does not necessarily follow that you will develop cancer. But knowing your syndrome status will empower you to take critical steps to help prevent cancer from occurring, to help detect cancer in its early stages, and to help you and your loved ones to make the right decision.

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Reason to Hope

There is new research from Brigham and Women’s Hospital that indicates a Western-style diet that is rich in red and processed meat, sugar and refined grains/carbohydrates is tied to higher risk of colorectal cancer through the intestinal microbiota.  Gastroenterology, 2022;DOI:10.1053/j.gastro.2022.06.054 

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