Is cancer in your DNA?

From CNET Magazine: Our genes determine our hair and eye color and -- in some cases -- our chances of getting cancer. Here's what you need to know.

Marguerite Reardon Former senior reporter
Marguerite Reardon started as a CNET News reporter in 2004, covering cellphone services, broadband, citywide Wi-Fi, the Net neutrality debate and the consolidation of the phone companies.
Marguerite Reardon
5 min read
Each color shows a chemical component of DNA. Getty Images

Looking at me, you wouldn't think I have much in common with Hollywood A-lister Angelina Jolie. But you'd be wrong. We both carry a BRCA gene mutation, giving us a high risk of developing the cancers that killed our mothers and grandmothers.

The BRCA1 and BRCA2 human genes normally produce proteins that prevent tumors. But when these genes change, or mutate, they can lose the ability to repair damaged DNA. Women who have inherited these genetic mutations have a much higher risk of developing breast cancer and ovarian cancer. Men also have an increased risk of breast and prostate cancers. And men and women both have a greater chance of getting melanoma and pancreatic cancers.

My mother, grandmother and my mother's aunt were all diagnosed with breast cancer in their mid-40s. My mother died at 59 of pancreatic cancer. At least eight members of Jolie's family have been diagnosed with a cancer that's likely linked to the BRCA1 mutation, including her mother, grandmother and aunt.

At stake is whether people with these genetic mutations will live to see their kids grow up. The good news is that prophylactic surgeries to remove ovaries and breasts can reduce the risk of breast and ovarian cancers by at least 90 percent, according to the National Cancer Institute. That's better odds than for the general population.

But this kind of preventive surgery is a deeply personal choice. Jolie chronicled her bilateral mastectomy and oophorectomy (ovary removal) in The New York Times. I had my oophorectomy last spring and plan a bilateral mastectomy in the coming months. Women who choose not to remove body parts can still benefit by having frequent screenings, since that increases the odds of early detection.


The White House glows pink in honor of Breast Cancer Awareness Month.


Hard choices

People with strong family histories of BRCA-related cancers easily meet insurers' criteria for covering tests that can cost thousands of dollars.

But what about those whose histories show few signs of the mutation?

Several companies in Silicon Valley are working to make genetic tests a lot more affordable. Color Genomics and Counsyl, for example, offer full gene sequencing of more than two dozen genes at a fraction of the cost. For a mere $250, anyone can be screened by Color Genomics for 30 genes, which can have thousands of known gene mutations. Counsyl's product costs $350.

"When the test costs thousands of dollars, it's hard to rationalize wide-scale testing," says Othman Laraki, president and co-founder of Color Genomics. "But the math on how many people we can test changes if we change the cost in a dramatic way."

This focus on predicting life-altering illnesses is leading to major breakthroughs in the treatment and early detection of cancer and other diseases. But experts warn that, without proper understanding, such information could cause more harm than good.

"We come from a society that tends to think that knowledge is power," says Jehannine Austin, president of the National Society of Genetic Counselors. "But information also has the potential to mislead and cause harm."

Testing for all?

At $250 a pop, these tests aren't much more expensive than other routine screenings, like Pap smears or mammograms. So why not test everyone? That's exactly what experts like Mary-Claire King, the geneticist who identified the BRCA1 gene in 1990, believe. She suggests every woman starting at age 30 be screened for genes that may play a role in breast and ovarian cancers.


Mary-Claire King, discoverer of the BRCA1 gene, receives the National Medal of Science award from President Barack Obama, May 2016.

Drew Angerer, Getty Images

"The fact that the test is affordable has huge implications for how we screen people," agrees Pamela Munster, co-director of the Center for BRCA Research with the University of California at San Francisco.

Four years ago, when Munster was diagnosed with breast cancer at age 48, she discovered she carries the BRCA2 mutation. A few months later, her father complained of abdominal pains. It turned out to be pancreatic cancer. He carries the mutation, too.

"If I had never been tested, we might not have put it together," she says.

But while cheaper genetic testing sounds great, the reality is that genetics is a tricky business. Tests can often reveal what geneticists call "variants of unknown significance."

"The problem with testing everyone is that not all genetic variations we can find, we know how to interpret," says Austin. "You can get variations that we simply don't know what they mean."

Fed crackdown

There's also the question of whether tests are valid and understandable.

Three years ago, the Food and Drug Administration stopped 23andMe from selling kits to consumers that claimed to detect their risk for breast cancer, Alzheimer's and other diseases, without proving the results were accurate.


The 23 pairs of human chromosomes, shown in a repeated pattern.

Science & Society Picture Library, SSPL via Getty Images

When 23andMe relaunched in October 2015, it no longer tested for genetic risks of disease. The company's test now provides information on genes for hair color, lactose intolerance and ancestry. It also provides genetic carrier information, which can reveal if parents could pass on genetic variances for illnesses like cystic fibrosis, sickle cell anemia or Tay-Sachs to their children.

"Genetic information is complicated, but that doesn't mean that it can't be made simple and understandable," says Erynn Gordon, 23andMe's medical marketing director.

The FDA says it's not trying to stop consumers from getting access to this information. It just wants to make sure the tests sold to consumers do what companies claim they do, and that the limitations and risks of the tests are made clear.

"I don't think consumers understand which tests have been looked at by the FDA and whether such tests are accurate and truthful in their claims," says Alberto Gutierrez, director of the FDA's Office of In Vitro Diagnostics and Radiological Health. "We know there are companies out there making lots of claims that are probably not sustainable. And that's why we'll be looking more closely at all these labs."

Companies like Color Genomics and Counsyl do not sell directly to consumers. Counsyl's test is ordered through a doctor. Color Genomics' test can be ordered online, but requires a doctor's prescription. Both companies strongly recommend genetic counseling as part of the process. Color Genomics offers counseling with one of its contracted professionals as part of its $250 price tag.


See more stories from CNET Magazine.

Michael Muller

At the end of the day, experts say that family history is still the most effective tool in figuring out who might be susceptible to a genetically linked disease and who won't.

"One of the most important things I need to learn about my patients is their family medical history," says Dr. Theodora Ross, an oncologist at the University of Texas Southwestern Medical Center.

"People need to talk to their families," she says. "It could save lives." 

This story appears in the fall 2016 edition of CNET Magazine. For other magazine stories, click here.