“What's the point of eating healthy, exercising and losing weight if a 'cancer gene' is inside me?”
Who among us hasn't worried about questions like these from time to time?
The National Cancer Institute makes it clear: Cancer is a genetic disease. Something's gone wrong with a person's DNA. A mutation, or series of mutations, has triggered abnormal, uncontrolled cell division and growth.
But tell people that cancer is “genetic” and many think back to their high school classes on DNA and start to wonder: "Do I inherit cancer the same way I inherited my mother's green eyes?"
No, you don't. Almost never.
Bad Behavior and Bad Luck
Cancer that runs in families is rare, making up only 5 to 10 percent of all cases.
City of Hope clinical geneticist Thomas Slavin, M.D., assistant clinical professor in the Division of Clinical Cancer Genetics, says that the rest can usually be blamed on two things:
“Risk factors. And bad luck.”
City of Hope clinical geneticist Thomas Slavin, M.D.
By far, most cancers occur because of something risky we did, or something risky we were exposed to. Think smoking and lung cancer. Workplace asbestos and mesothelioma. Obesity and, well, lots of things.
These so-called risk factors damage our genes, making a mutation — and cancer — more likely (though not inevitable). And, while there are no guarantees, avoiding risk factors or proactively minimizing them goes a long way toward preventing many cancers from developing.
But that doesn't mean you give up.
“Working on risk factors can modulate your bad luck,” said Slavin. “Sometimes only slightly, other times more so. So do quit smoking. Watch your diet. Lose the weight. It matters.”
A Family Affair
But when does family history matter? Which cancers are inherited?
In the past decade, we've learned a great deal about hereditary cancers, and we're learning more all the time.
Thanks in large part to the successful mapping of the human genome, scientists can now pinpoint dozens of inherited mutations that predispose people to various forms of cancer. Perhaps the best known is the set of mutations on the BRCA1 and BRCA2 genes, which dramatically raise the risk of breast and ovarian cancer. The BRCA case is unique because it also carries an ethnic component, concentrated in the Ashkenazi Jewish community (Jews of Eastern and Central European descent).
Inherited cancers tend to show up early, because so-called “tumor suppressors,” the genetic elements that regulate cell growth, don't work properly from birth. So, if Great Uncle Max came down with colon cancer in his 80s, it's not necessarily a danger sign for his kids. However, if multiple relatives develop the same cancer at a young age, that could be a red flag.
And that's when family members should seriously consider genetic screening, and not fear the “bad news” they may hear.
“Even though it may seem overwhelming at first,” Slavin said, “the fact is, not everyone with a specific mutation develops cancer, just as the absence of a mutation is no guarantee you won't get cancer.”
What's more, if a mutation is discovered, there are prudent and potentially life-prolonging options.
Women with BRCA mutations for example, typically submit to “high-risk surveillance,” getting a mammogram or MRI every six months, to catch any tumors at an early stage. Other patients go a step further and have both breasts removed, which serves to reduce their breast cancer risk even below the general population.
As knowledge of cancer's genetic nature expands, so do the treatment options. Slavin says there are many 'actionable' gene mutations, meaning they can potentially be altered by targeted therapy drugs.
It's easier and less expensive than ever to undergo genetic testing, and more likely than ever that health insurance will cover the cost. Most important, since 2008 it has been illegal for insurers or employers to discriminate based on DNA test results, so much of the earlier stigma has disappeared.
What hasn't disappeared, is the reality of the human condition.
“In the last five years we've come to realize,” said Slavin, “that we all have mutations. We all have mutations our parents didn't have, and, from birth to death, our genetic makeup changes.”
Does that mean that everybody should have their DNA tested?
“We're not ready to roll that out yet.”
Nor does Slavin recommend relying on do-it-yourself DNA tests now commercially available. He strongly recommends working with a genetics professional to get the most thorough picture.
“Knowledge is power,” he said.
Stories of Hope is a monthly series that explores important issues in health care. During National Cancer Prevention Month, we’re taking a closer look at the science — and the psychology — behind cancer prevention.