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Code Check

Genetic testing can reveal if you or members of your family tree are predisposed to disease or birth defects. But basing health-care decisions on such information isn’t always clear-cut: DNA isn’t necessarily destiny.

Code Check
Photo by Harry Campbell (Illustration)

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Since the mapping of the human genome was completed, in 2003, genetic testing has exploded. Adults, children, and infants now can be screened for more than 1,000 genetic disorders, from well-known hereditary diseases, such as hemophilia and sickle cell anemia, to more common medical conditions, such as cancer, heart disease, diabetes, and Alzheimer’s. ¶ Recommendations about who should be screened—and for what—are updated frequently. Minnesota’s newborn screening program now tests for 53 conditions. Earlier this year, the American College of Obstetricians and Gynecologists recommended that all pregnant women undergo prenatal testing for Down syndrome. ¶ But the amount of new data can be overwhelming—particularly for women who serve as “information caretakers” for others, says Mary Ahrens, a genetic counselor at the University of Minnesota Medical Center–Fairview. ¶ Happily, you don’t need to have aced high-school biology to understand the choices that come with gene screening. Here’s what the tests may mean for your and your family.

Improving the Odds

A dozen years ago, surgery was the surest way to sidestep the risks associated with hereditary breast cancer. Today, thanks to DNA TESTS, women can better assess the dangers they face.

No genetic test for breast cancer existed in 1995, the year Jane Legwold had both her breasts “lopped off,” as she puts it, to lower her odds of developing the dreaded disease. Not until the following year did testing for abnormalities on the two major breast-cancer genes, BRCA1 and BRCA2, become an option.

But Legwold already knew the odds of finding a malignant tumor in one or both of her breasts were off the charts. The women in her family had a history of breast cancer: a maternal aunt and a cousin had died from the disease, and Legwold’s mother and two older sisters had been diagnosed and treated for it. Based on that legacy, doctors gave Legwold a 50-50 or greater chance of becoming one of the more than 210,000 women diagnosed with breast cancer each year in the United States.

Legwold, a psychotherapist who had gone through nursing school, was understandably worried—not just for herself, but also for her two young children. Then in her forties, she didn’t want to risk leaving them motherless. Test or no test, she decided to have her healthy breasts surgically removed. Then, as now, the procedure—prophylactic mastectomy—was controversial. But studies have since shown that such surgery can reduce a woman’s chance of developing breast cancer by as much as 95 percent.

Today, genetic testing is routinely offered to women with a family history of breast cancer. Not all opt to take the test, however. “Some women want to know [whether they have an altered BRCA gene], but others don’t. It’s just too scary for some,” explains Mary Ahrens, genetic counselor at the University of Minnesota Medical Center–Fairview. Ahrens helps people evaluate the risks, but leaves decisions to them: “I tell patients, ‘It’s your choice. We’re not here to tell you what’s best for you or your family.’”

Photo by Eric Moore

Most breast-cancer cases—at least 90 percent—are not linked to abnormal BRCA genes, but having one of these mutations greatly increases a person’s cancer risk. Women in the United States typically have about a 12 percent chance of developing breast cancer if they live to age 90. For women with an abnormal gene, that risk increases to 85 percent.

When considering any genetic test, Ahrens says it’s important for women to ask themselves if the results would cause them to make changes in their care?

Legwold says her answer would have been a resounding “no.” She would have had her breasts removed even if her BRCA tests had been negative. She wanted peace of mind.

But for other high-risk women, prophylactic surgery is simply not an option. Knowing that they carry a BRCA gene abnormality might move them to have mammograms and breast exams regularly—but the news could also trigger feelings of anxiety, depression, or anger. Ahrens says women are sometimes traumatized to learn they carry a BRCA gene mutation—often because they are worried the mutation will be passed on to their daughters.

A normal finding doesn’t guarantee healthy genes, however. Some women may carry a mutation that’s either not yet identified or not detectable by the current method of testing. Last year, a University of Washington study found that the most widely used genetic test for breast-cancer risk missed less-common gene mutations in about 12 percent of cases.

So what should women do if they have a family history of breast cancer? Ahrens recommends seeking counseling so you can understand your risk more clearly before you make a decision about genetic testing (see sidebar for further recommendations). Often, women are surprised by what they learn.

“Sometimes women underestimate their risk,” says Ahrens. “But they’re more likely to overestimate it.”

A good genetic counselor can help ease your mind—and offer information regarding medical choices. “Knowledge is good,” Ahrens says. “Knowledge is power.”

In 2001, six years after having her mastectomy, Legwold received the results of tests on blood samples that she and family members had provided to researchers years earlier, before such testing was possible. No BRCA gene mutations were found. “I didn’t give a rip,” says Legwold, “because I knew I had done the right thing. I’m still not convinced cancer isn’t in the family. I felt like I was a sitting duck for it. It wasn’t a matter of if I was going to get breast cancer, but when.”

To Test or Not to Test?

The U.S. Preventive Services Task Force recommends that you receive genetic counseling to determine your breast-cancer risk if you fall into any one of the following categories:
• You have more than one first-degree relative (mother, sister, or daughter) with breast or ovarian cancer.
• You have more than one second-degree relative (aunt, grandmother, or cousin) with breast or ovarian cancer.
• You have a first- or second-degree relative who was diagnosed with breast or ovarian cancer before the age of 51.
• You are of Ashkenazi (Eastern European) Jewish heritage.

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