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A man curious about his cancer risks gets a mouth swab for genetic testing.

Is genetic testing necessary for finding out cancer risk? An oncologist weighs in.

Posted in: Blogs

When the body’s cells grow and divide in ways that our systems can’t manage, they become cancerous. Lifestyle and environmental factors can influence these changes, but our changing genes also play a crucial role in determining an increased risk of developing cancer. We spoke to Dr. Alastair Thompson, co-director of the Lester and Sue Smith Breast Center at the Dan L Duncan Comprehensive Cancer Center, about genetic testing and how it can help educate and prepare patients about their cancer risks.

What is genetic testing?

Genetic testing is the use of medical tests to locate specific gene mutations in people. There are many ways to use genetic testing; one of them is finding gene changes linked to cancer.

Examples of cancer genes include BRCA1 and BRCA2. Normally, the BRCA1 and BRCA2 genes protect you from certain cancers, but mutations can keep them from working properly. Three percent of breast cancers and 10% of ovarian cancers result from mutations in the BRCA1 and BRCA2 genes.

What are BRCA1 and BRCA2? 

These are genes that help repair damaged DNA by producing specific proteins. Everyone has two copies of these genes, one inherited from each parent. When they change or mutate into harmful variants, they are called tumor suppressor genes.

How is genetic testing useful in learning about cancer risk?

Genetic testing can be practical in helping give you an estimate of whether you have the chance of developing cancer in the future. Dr. Thompson elaborates, “genetic testing can identify genes inherited from our parents and, depending on the exact gene, change may put some numbers on the risks of cancer.”

Genetic testing is also helpful in determining if you have hereditary cancer syndrome, which involves the mutations of genes passed from parents to children.

What is hereditary cancer syndrome? 

An inherited condition in which there is a much higher risk for certain cancers. Examples of hereditary cancer syndromes include hereditary breast cancer and ovarian cancer.

Other examples of cancers influenced by specific genes include the following:

Breast cancer

Pancreatic cancer

Prostate cancer

Ovarian cancer

Colorectal cancer

When should you get genetic testing?

“If you have a diagnosis of cancer yourself,” recommends Dr. Thompson, “or if you have had a relative diagnosed with certain types of cancer. Genetic testing may allow you to decide what sort of preventive measure could be taken.”

Who are candidates for genetic testing?

Dr. Thompson notes that patients and their relatives who have had a cancer diagnosis before the age of 50 should look into genetic testing. “Particularly if other close family members have (had) cancer not necessarily in the same part of the body.”

Here are other characteristics one would need to consider genetic testing for cancer risks:

● Several types of cancer in the same individual

● Cancer is present in both organs in a paired set (kidneys, lungs, breasts, or ovaries)

● Several relatives with the same kind of cancer.

● Relatives with breast cancer, ovarian cancer, colon cancer, or endometrial cancer.

Does someone carrying cancer genes always get cancer?

Although a cancer susceptibility variant exists in a family’s genetic history, this doesn’t always mean descendants who inherit the gene will develop cancer later on.

“The good news is that even if you have a cancer susceptibility gene, you may still avoid getting cancer. That is why the decisions around what to do if you have a gene are so difficult, and you can benefit from discussing with a genetics counselor or clinicians with knowledge and expertise of genes and cancer.”
—Dr. Thompson

Many factors influence how an individual could develop cancer. Inherited cancers can vary in how they express signs and symptoms, and not all people who carry the cancer gene end up getting cancer.

What is involved in genetic testing for cancer?

Genetic testing begins with a consultation with a genetics counselor or doctor who will evaluate a person and their family history. “Usually, a blood sample or sample from a mouth swab are used to do the testing for cancer susceptibility,” says Dr. Thompson, “You need to get the results of the test and discuss what they imply. If there is no genetic risk from the gene testing, that is clearly better news than detecting an abnormality which might lead to you having screening tests from a younger age or more frequently than a standard member of the public.”

What genetic testing services or capabilities are available at St. Luke’s Health?

“We have great and knowledgeable genetics counselors who meet with the individual, map out the family tree and then offer testing for inherited genes (usually on a blood sample or mouth swab) that might predispose to cancer. In addition, for those who have had cancer, cancer itself can be tested for genes that might offer newer treatment options.”
—Dr. Thompson

The Dan L Duncan Comprehensive Cancer Center (DLDCCC), a department of Baylor St. Luke’s Medical Center, provides exceptional care to patients from all over the world. DLDCCC is one of only three NCI-designated Comprehensive Cancer Centers in Texas and the site of the largest clinical genetics program in the nation. If you or someone you know faces a cancer diagnosis or is at an increased risk of developing cancer, reach out to our specialists at (713) 798-1999 today. Our team combines compassion and kindness with precision medicine and nationally accredited cancer care, leading research, and innovative treatment options. Talk to your primary care physician about your potential genetic predisposition to cancer today.

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