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Busting Myths About Your Genes and Breast Cancer

posted on 12/26/2016 Facebook Facebook

For starters, how common is genetic breast cancer?

“I look just like my mother and grandmother, and they both hadbreast cancer. So I’ll have breast cancer, too.”

Is the statement above based on myth or fact?

Answer: Myth. The genes that affect your physical traits aren’tthe same ones that affect your breast cancer risk.

But the statement does bring up important follow-up questions.Did your mother and grandmother have breast cancer at a young age? Did otherfamily members have breast cancer, too? Was their breast cancer confirmed asbeing genetic? These are all important red flags, unlike physical appearance.

That statement is just one myth among many in the world ofbreast cancer and genetics. Below are a few more — along with the facts youshould know instead.

Myth: Most breast cancer is genetic

Blazer: In truth, about 10 percent of all female breast cancersare caused by “strong” inherited genetic mutations. Men get breast cancer,too, but we don’t have an accurate number for how many cases are geneticbecause the rate of cancer is quite a bit lower.

So, around 1 in 10 cases of female breast cancer relate togenetic mutations. That’s a high enough percentage that we encourage all peopleto keep a good family medical history and watch for red flags. But italso means 9 out of 10 cases aren’t related to your genes.

Myth: The BRCA genes are the only genes related torisk

Blazer: You’ve probably heardof BRCA1 and BRCA2 genes. They’re the most common genesinvolved in breast cancer, so they get the most coverage. A mutation in thesegenes raises your lifetime risk of developing breast cancer to as high as 85percent.

But there are other genes with strong links to breast cancer,too. For example, P53 mutations — while less commonthan BRCAmutations — can lead to an even higher lifetime risk.

There are currently 10 genes in total with strong connections tobreast cancer risk: the three aboveplus NF1, SDHB/D, KLLN, PTEN, STK11 and CDH1.Often these genes are tied to other cancers but do raise your risk of breastcancer, too. For example, PTEN is connected to Cowden syndrome, whichhas a high risk of breast, thyroid and other cancers. CDH1 is tied togastric cancer but also has a high risk of lobular breast cancer.

If this seems like a confusing mess of alphabet soup, neverfear: That’s what genetic counselors are for. If you have red flags forgenetic cancer — such as an early age of diagnosis, two or more differentcancers or multiple family members who have had cancer — ask about a referralfor genetic counseling.

A genetic counselor helps determine exactly whatscreenings you may need, puts test results into context and helps guide you tonext steps, from treatment to high-risk monitoring.

Myth: Not everyone has these genes

Blazer: Actually, everyone does have two copies of these genes(a pair of working genes). Whether you’re a man or woman, youhave BRCA, P53, all of the above.

You just don’t necessarily have a mutation in thesegenes. It’s the mutation — not the gene itself — that leads to cancer risk.

Think of these genes as editors. They search through the massiveamounts of data in your cells looking for errors. When they have a mutation,they can no longer edit properly. That’s when mistakes multiply, and cancergrows and spreads.

Myth: If you have a mutation, you will automatically get cancer

Blazer: It’s true that if you have a mutation, you have a higherrisk of developing breast cancer during your lifetime. But a mutation does notguarantee you will develop cancer.

For one thing, if you know you have a mutation, you can act onthat information. You’ll work with your doctors on a plan for monitoring andprevention. In the highest-risk cases, that may mean discussing options suchas preventive surgery, too.

But beyond that, not everyone with a genetic mutation hasexactly the same lifetime risk. The next step in medical research isfine-tuning our risk assessments. For example, with a BRCAmutation, we wantto know exactly who has that high 85 percent lifetime risk and whose risk maybe lower, based on other factors. That’s the future, and it may be closer thanyou think.


Myth: I look just like my mother and she had breast cancer, soI’m certain to get it, too.

Blazer: “That’s not how genetics work. These traits aren’tnecessarily linked. Even though you inherited certain genes that govern yourphysical appearance, there’s still a chance that you didn’t pick up themutation that increases cancer risk.”

Myth: As a man, I don’t have to worry about inherited breastcancer in my family.

Blazer: “A male with a BRCA mutation does have increased cancerrisk — it’s just not as high as for women. Male breast cancer is rare, but thismutation increases risk 100-fold. It goes up to about 6 or 7 percent lifetimerisk, which is still less than a woman’s average risk.  Prostate cancerand pancreatic cancer risk can be increased as well.”

Myth: The breast cancer is on my father’s side of the family, sothere’s nothing to worry about.

Blazer: “This is a common misconception among both patients andmedical professionals. In reality, single-gene traits like BRCA mutations arepassed down equally by males and females, so we all need to consider the cancerhistory on both the maternal and paternal sides of the family.”

Myth: There’s no personal benefit to genetic testing in cancerpatients like me.

Blazer: “A lot of people think, ‘I’ve already gotten the cancer.The lightning has struck already. I’m doing this for my sister, my niece, mydaughter.’ But we tell them, ‘There are implications for your care goingforward.’ Patients with a hereditary predisposition have a much higher risk toget a new primary cancer in another place — not a recurrence, but a newcancer.”

Myth: If I test negative for BRCA-1 and 2, I’ve got nothing toworry about.

Blazer: “A negative test result doesn’t mean there isn’t risk.You’ve looked at one or two genes at a certain level of technical sensitivity.There could be something else that they weren’t looking for. We know othergenes are involved in breast cancer, but we haven’t identified some of theseother genes or fully characterized their significance to levels of risk forbreast or other cancers yet.

“For example, if you had a sister who had breast cancer at 32and a mom who died of ovarian cancer at 52, and you’re an unaffected35-year-old who’s being told ‘You’re free and clear,’ we’d be very concernedabout that type of interpretation.

“You have to go back and do your screening and management basedon the family history. You really want to seek out counseling with someonewho’s been trained in cancer genetics.”



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