Skip to Content


Genetic Testing: What Patients Should Know

Network - Winter 2011

By Mary Brolley

When Banu Arun, M.D., explains her work, she starts with the basics.

An expert in genetics — specifically the genes involved in mutations that raise the risk of breast and ovarian cancers — Arun is a professor in the Department of Breast Medical Oncology and co-director of the Clinical Cancer Genetics Program at MD Anderson.

First, she notes that a person’s lifetime risk of cancer is one out of two for men, one out of three for women. To add context, she might add that in 2010, an estimated 1.5 million Americans were diagnosed with cancer.

Of those who do get cancer, only 5% to 10% will do so by inheriting a mutated gene.

In fact, nine out of 10 people who develop cancer do so simply because they:

    • get older

    • fit into a higher-risk category due to smoking, obesity or alcohol abuse

    • have a predisposing condition such as HIV infection 

    • have any combination of these factors

Still, for the small proportion of patients at risk of inheriting cancer, genetic testing is an area of growing awareness and interest.

Genetic testing involves taking a blood sample. It may take several weeks to get the results. Though some patients worry that test results might be used against them, Health Insurance Portability and Accountability Act provisions prohibit group plans from using genetic information to determine eligibility or establish a preexisting condition.

Arun believes that before deciding whether to undergo testing, people should first speak with a genetic counselor.

“They’re specially trained to do a risk assessment with a patient,” she says. “And deciding to see a counselor doesn’t mean you have to go through testing. They’ll discuss the benefits and limits of being tested in each case.”

“For example, only about 10% of breast cancer types are inherited. The rest are what we call ‘sporadic’ — that is, they occur because of a confluence of factors.”

But what if there is a family history of cancer?

First, make a family tree

Sketch out your birth family, noting whether anyone was diagnosed with and/or died of cancer, and at what age. Then go back as far as you can, filling in as many details as possible on earlier generations.

The red flags for hereditary predisposition are finding relatives who contracted cancer before turning 50 years old and/or had more than one primary cancer. 

Other warning signs are many family members with the same or a related cancer and multiple generations affected.

A positive result carries big weight because it means the person has a greater lifetime risk of developing cancer, and doing so at a younger age.

The best person to test is likely the person with cancer, Arun says. “Once we identify the mutation that caused her cancer, we can test first-degree relatives — mother, sisters, daughters — to see if they also carry it.”

Among the most common hereditary mutations are BRCA1 and BRCA2, which have been identified as breast-ovarian cancer susceptibility genes.

“It can be helpful for women to know their gene status before beginning treatment,” she says. “For example, a woman identified as carrying one of the BRCA mutations might consider a range of options, from treatment for the affected breast and surveillance on the other, to a prophylactic mastectomy.

“And once a woman knows she has the mutation, she can get more intensive screenings, including those for ovarian cancer, earlier.”

Though it’s her passion — her calling — Arun knows that genetic testing isn’t the answer for every cancer patient.

Limits, benefits of testing

The tests can only provide information about a person’s risks of developing this type of cancer.

Not all of the genes associated with hereditary cancer have been identified. Not all gene mutations may be detectable. Results can be inconclusive. And costs, which range from hundreds to thousands of dollars, might not be covered by insurance.

But for some patients, the tests provide crucial knowledge. Those who test positive for a known cancer-causing mutation might find that their initial disappointment and dread are followed by a resolve to meet the risks head-on with increased vigilance and enhanced screening.

In families that carry the mutated gene, those who test negative are relieved that their health and that of their children is less at risk.

Arun says that even these clients contribute to the Clinical Cancer Genetics Program’s research, which includes identification of new chemopreventive agents and several Phase II prevention studies.

“A number of young women we test agree to let us keep their blood samples for research. We’re so thankful for that,” she says.

© 2015 The University of Texas MD Anderson Cancer Center