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.
The Price of Knowledge
Genetic tests can help couples weigh whether to have children. But the hardest decision is often whether to get tested at all.
The pre-wedding to-do list of Christina Schlemmer, 25, includes the usual tasks: Mail the invitations. Make sure the bridesmaids get fitted for their gowns. Double-check the honeymoon reservations.
But also on this bride-to-be’s list is an item rarely suggested by professional wedding planners: schedule a genetic-testing appointment for the fiancé.
Schlemmer, of St. Paul, has cystic fibrosis (CF), an incurable genetic disease that affects breathing and digestion. Just a few decades ago, few children with CF lived past their elementary-school years. Today, thanks to new treatments, many people with CF lead active, productive lives into their thirties, forties, and beyond.
Those same medical advances have made it possible for some women with CF to have successful pregnancies. Schlemmer, whose CF symptoms are relatively mild, hopes to have two or three children.
Genetic testing will help her and her fiancé prepare for parenthood, says Schlemmer, especially if the children have CF. The disease is not always passed on from mother to infant. For a baby to be born with CF, both parents must carry a copy of the defective CF gene. If her fiancé, Nick Doffing, is one of the 10 million Americans who are symptomless carriers of the defective CF gene—as both Schlemmer’s parents are—any child born to Doffing and Schlemmer would have a 50-50 chance of having CF.
Screening for genetic carriers has grown in recent years. CF tests are now routinely offered to all couples planning a pregnancy, not just those with a family history of the disease. Other common genetic tests given to prospective parents include those for sickle cell anemia, muscular dystrophy, and Tay-Sachs disease.
Photo by Eric Moore
“Many couples have genetic testing because they want information, but they may be very unsure at that point what they want to do with it,” says Noralane Lindor, MD, a professor in the genetics department at the Mayo Clinic College of Medicine.
Undergoing genetic counseling before gene screening can help couples decide whether they even want the information. “One of the major misconceptions I encounter is that we’re always pushing people to do the testing,” says Matt Bower, a genetic counselor at the University of Minnesota Medical Center–Fairview. That’s untrue, he says. “I’ve had innumerable instances where I’ve helped people decide that testing really wasn’t in their best interest,” he says.
If a prenatal test comes back positive for a genetic disorder, some women use that information to prepare themselves emotionally and otherwise to care for a child with a disability. Others, however, choose to end the pregnancy.
Schlemmer says that even if Nick is a carrier of the CF gene, it will not affect the couple’s choices. “It won’t matter,” she says. “I was three months old when my parents found out that I had CF. I just think it would be better to know from the start.”
Common Genetic Screening Tests
MANY GENETIC DISORDERS are autosomal recessive—passed on to children only if both parents are carriers of the genetic trait for that disorder. But if the parents themselves exhibit no manifestations of the disorder, genetic testing is needed to determine whether they are carriers. If tests show that both parents are carriers of a particular defect, they may opt for prenatal testing to determine if their fetus has the disorder. Children of two carriers have a 25 percent of inheriting the disorder.
The following are some of the autosomal recessive disorders that prospective parents are often tested for. Some genetic disorders are more likely to occur among people of particular racial and ethnic backgrounds.
Parents of African Background
• Sickle cell disease (carrier frequency: 1 in 12)
Parents of Ashkenazi Jewish Background
• Tay-Sachs disease (carrier frequency: 1 in 30)
• Canavan disease (carrier frequency: 1 in 40)
• Niemann-Pick disease type A (carrier frequency: 1 in 90)
• Gaucher disease type 1 (carrier frequency: 1 in 12)
• Bloom syndrome (carrier frequency: 1 in 100)
Parents of Caucasian Background
• Cystic fibrosis (carrier frequency: 1 in 25)
Parents of Mediterranean (Greek, Italian), Southeast Asian, and/or African Background
• Beta-thalassemia (carrier frequency varies with ethnic group)
Parents of Southeast Asian Background
• Alpha-thalassemia (carrier frequency varies, but may be as high as 1 in 20)
DNA 411
Questions and Answers Regarding Gene Screening
What kinds of genetic tests are available?
There are more than 1,000 genetic tests, which fall into several categories. Carrier screening determines if you (and/or your partner) carry a gene mutation for a disease that could be passed on. Prenatal diagnostic testing determines whether a fetus has a genetic disorder. Predictive testing helps you estimate your risk of developing hereditary disorders, such as some forms of breast cancer. If you’re already displaying symptoms of a genetic disease, diagnostic testing will help confirm that you have the disorder.
Who are genetic counselors?
They’re specialized health professionals who have completed a master’s program in medical genetics and counseling skills and who have been accredited by the American Board of Genetic Counseling. In addition to knowing the benefits and limitations of genetic screening, the counselors can help navigate emotional and ethical issues.
How do I find a genetic counselor?
The best way is to ask your physician for a referral. You can also locate a genetic counselor through the National Society of Genetic Counselors’ website: www.nsgc.org/resourcelink.cfm.
If I seek counseling, will I automatically be tested?
No. The decision to undergo genetic testing is very personal. Most genetic counselors recommend that you ask yourself what you would gain by being tested. Would you do anything differently if you discovered you carry a genetic mutation?
What does genetic testing involve?
For most genetic testing, you’ll be asked to give a small sample of blood, but cells from your hair, skin, or other tissues may also be used. For prenatal testing, cells are retrieved from amniotic fluid (amniocentesis) or the placenta.
Do the tests have any medical risks?
Prenatal testing poses a very small risk of miscarriage—no more than 1 percent, or 1 in 100 for CVS and perhaps as low as 1 in 1,600 for amniocentesis, according to new research. You’ll need to decide whether that risk is acceptable.
Susan Perry is a freelance writer who specializes in medical topics. She lives in Minneapolis.
