Can DNA Predict Your Cancer Risk?

Can DNA Predict Your Cancer Risk?

Tuesday, February 06, 2018

Cancer is one of the most common diseases we face today. About one in every two men—and one in three women—will get some form of cancer over the course of their lives. That means most families are directly impacted by the disease in some way.  

Has a family member of yours been diagnosed with cancer? Have you ever wondered, “What are the chances that I’ll get cancer?” How do you know whether cancer “runs in the family” or stems from other factors like aging, lifestyle or the environment? Genetic testing can help answer these questions. 
Using saliva or a small blood sample, DNA tests can tell whether a person is predisposed for developing hereditary cancer or whether a patient’s particular cancer could be passed on to children. 
Fewer than 10 percent of cancers are caused by a gene inherited from the patient’s mother or father. While that’s a seemingly low number, finding out whether you carry the hereditary cancer gene can ease your worries, or it can allow you to manage your risk of developing genetic cancer. 
For cancer patients facing a new diagnosis, genetic testing can ensure that doctors make the best treatment or surgical decisions based on the specific cancer, and it also allows family members to better understand their risk of developing the disease. 
Genetic testing results can help women with breast cancer decide whether they want to have a lumpectomy versus a mastectomy. The results can influence what type of chemotherapy a patient gets, and they can determine when you should start getting screenings like mammograms or colonoscopies (and how often). Through more frequent monitoring and beginning it earlier, physicians are able to catch things at the pre-cancerous stage, and prevent them from ever actually becoming cancer.

Testing for Hereditary Cancer

Genetic testing for cancer risk gained public attention a few years ago when celebrity actress Angelina Jolie discussed her family history of cancer and her choice to pursue genetic testing. Jolie was found to have an increased risk for breast and ovarian cancer based on her BRCA1 gene. To reduce her risk for these cancers, she elected to have a bilateral mastectomy and ovarian removal before cancer ever occurred. 
BRCA1, and its partner, BRCA2, are two of the most well-known causes for hereditary breast and ovarian cancer. Together, they explain approximately 50 percent of these cancer cases. But what about the other 50 percent? Scientists have identified 18 additional genes that can increase the risk of breast and ovarian cancers—that’s 20 total genes you can be tested for to determine your risk for hereditary breast and ovarian cancer. 
With our understanding of the human genome, genetic testing has become increasingly complex. For help navigating the complicated world of cancer, family history and genetic testing, it’s best to visit an oncology-trained genetic counselor. They can help you weigh the pros and cons of various testing options to determine whether testing is right for you and which genetic tests you should consider based on your medical history information. 
Many cancer types can be associated with a genetic cause. For example, one gene can cause an increased risk for breast cancer, ovarian cancer, pancreatic cancer and prostate cancer. Even within the same family, people who carry the same genetic risk might show it differently. One family member might get breast cancer, another could get prostate cancer, and yet another might never develop cancer but could pass the gene on to a child, who might develop two types of cancer. Genetic counselors are specially trained to look at your family history and identify any patterns that can help guide genetic testing decisions. 
Genetic counselors will review possible testing outcomes with you and will explain what the results could mean for you and your family. As experts in genetics and how they impact cancer risk, counselors will talk about what you can do to reduce potential cancer risks.  
If you have a family history of endometrial, colon, or other gastro-intestinal cancers, genetic testing can be helpful as well. These cancers can all be seen in Lynch Syndrome, the most common cause for hereditary colon cancer. Depending on your personal and family history of cancer, you can be tested for over 30 different genes that can shed light on why these cancers have occurred and who in your family is at risk. 

If you or a relative have had any of the following, you might benefit from genetic counseling and testing: breast cancer before age 45; two or more breast cancers, bilateral breast cancer or male breast cancer; ovarian cancer; endometrial (uterine) cancer before age 50; two or more cancers; colorectal cancer before age 50; Ashkenazi Jewish heritage; a family history of breast, colorectal, endometrial, ovarian, small bowel, stomach, pancreas, bladder or thyroid cancer.

Taking the First Step

The first step toward understanding your hereditary cancer risk is making an appointment with a genetic counselor. You can ask your doctor for a referral or call Sarasota Memorial Cancer Institute’s genetic counseling team with any questions or to make an appointment (941-917-2005).  

Before your appointment, collect information about your personal and family medical history: Who in your family has had cancer? Where was the cancer (breast, colon, etc.), and how old was your relative when they were diagnosed? 
Genetic counseling appointments usually take about an hour. During your visit, you can expect:  

• A discussion about your personal medical history, and an in-depth look at your family’s medical history. This helps determine whether you are high-risk and meet testing criteria.  

• An explanation of the pros and cons of the testing options, the possible test results, and how they may impact you and your family members.  

• A discussion about the types of cancers associated with hereditary cancer syndromes, the potential risks associated with them and ways to help you lower your cancer risk.  

Help with any health insurance issues you may encounter. It can take up to three or four weeks to get test results. The genetic counselor will go over them in detail with you and will answer any questions you may have. You’ll also receive a written letter summarizing your genetic testing results for you to share with your family and doctors.  
If you have any questions, or would like to schedule a genetic counseling appointment, call (941) 917-2005. You can find more information on genetic counseling, testing and SMH’s program by visiting


Genetic Counselor Nicole WoodNicole Wood, MS, CGC, is the only licensed and board-certified genetic counselor serving Sarasota County and its surrounding communities. Specialty trained in oncology genetic counseling, Wood works closely with a multidisciplinary team at Sarasota Memorial Hospital to provide expertise for patients’ clinical care. She contributes regular blog posts on topics related to genetic testing, counseling and hereditary cancer syndromes.