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Breast Cancer: The Genetic Risk

Breast Cancer: The Genetic Risk

By SMH Certified Genetic Counselor Nicole Wood

Cancer—especially breast cancer—often seems to run in families. This could be because the relatives share certain lifestyle habits, or because they live in the same area and have the same environmental exposures. Occasionally, though, the cancer can be inherited—a mutation in the genetic code that is passed down from generation to generation.

Cancer is complicated. Even with all of the medical advances we have made, doctors still cannot pin-point exactly what causes a person’s cancer.

Most cancer is considered sporadic, caused by many factors that accumulate over the years. In fact, aging is the number one risk factor for all cancers. A person’s risk also can be increased by environmental factors or lifestyle habits, like smoking and inactivity. At the same time, we also all have genes that work hard to keep us cancer-free by interacting with all of these outside factors. 

A good analogy for cancer is like filling a cup with water: When the cup overflows, the body has cancer. Was it the first drop of water that caused it to spill over, or the last? Most people begin life with an empty cup, and it gradually fills as time goes on. However, 10 percent of cancers are inherited, meaning that a person can start life with their cup partially filled.

BRCA & Beyond

You might have heard of the BRCA1 and BRCA2 genes, which can greatly influence a woman’s risk for breast and ovarian cancer. BRCA1 and BRCA2 are among the many cancer-fighting genes that we all have. But when these genes are faulty, broken or mutated in some way, they can increase cancer risk. We can inherit these genes already broken from either our mother or father (who inherited the mutations from their mother or father, who got them from their mother or father, and so on).

Certainly, BRCA1 and BRCA2 are the most well-known and well-studied genes related to breast and ovarian cancer right now. Until as recently as 2013, they were essentially the only genes you could be tested for to determine whether you or a relative were predisposed to breast cancer. But as technology and science have evolved, researchers have continued to learn more about the human genome and how our genes can impact our health. In fact, we can now test for 18 other genes identified as increasing the risk of breast and ovarian cancers—that’s 20 genes you can be tested for to determine your risk for breast and/or ovarian cancer!

Not all of these cancer-risk-indicating genes are equal in terms of severity. While having BRCA1 and BRCA2 mutations represent a very high chance of developing breast cancer, some of the other genes we test represent a much lower, 20-percent chance. In addition to genetic makeup, a woman’s family history can provide the biggest clue as to where her individual cancer risk truly falls.

What Does an ‘Increased Risk’ Mean?

Every person has a chance of developing cancer in their lifetime. Because cancer is unfortunately such a common disease and we are living such long lives, it’s estimated that 1 in 2 men and 1 in 3 women will develop cancer in their lifetime.

The average woman has a 1 in 8, or 12.5-percent, chance of developing breast cancer in her life. So, if you follow the lives of 100 women, 12 to 13 of those women will eventually develop breast cancer. But if you follow the lives of 100 women who have inherited a broken BRCA1 gene, for example, 60 to 85 of them will eventually develop breast cancer. 

What Can I Do if Cancer Runs in My Family?

If you are worried that cancer seems to run in your family, talk to a genetic counselor specializing in oncology. Genetic counselors have specialized, graduate-level training in medical genetics and counseling. Armed with all of the most up-to-date information on new genes, associated cancer risks, and health-insurance regulations, the genetic counselor can guide you through every step of the evaluation, and if need be, the genetic-testing process. (You can ask your doctor for a referral to a counseling program or visit the National Society of Genetic Counselors website to find a qualified local genetic counselor.)

A genetic counselor will review your personal medical history to identify any individual risk factors, such as pregnancy history, smoking history, how much you exercise, and of course whether you have had cancer before. They will also take a detailed family history. This allows the genetic counselor to get a bigger picture of your personal family, and to see if the cancers may be hereditary or sporadic.

Hereditary cancer and sporadic cancer act differently in families. Sporadic cancers tend to occur at older ages (remember, aging is the Number One risk factor), and will happen randomly within a family tree. Hereditary cancers seem to affect multiple generations, with similar or connected cancers affecting family members and occurring at younger ages, usually under 50.

Depending on the counselor’s evaluation of your personal health and family medical history, he / she might recommend genetic testing or a health-maintenance routine. 

What happens if I test positive?

The benefit to genetic testing to find out if you have a cancer predisposition is that with today’s technology, we have the ability to help prevent you from developing the disease. Breast cancer, in particular, is a disease that we know a lot about screening for and preventing. When someone is found to have a gene mutation that gives them an increased risk for breast cancer, several steps can be taken to reduce the risk. Which steps are taken depends on many factors—the most important of which is the individual. These are all personal choices, and no two people will choose exactly the same path for exactly the same reasons.

Surveillance: For an average woman, mammograms are recommended every year beginning at age 40 to screen for breast cancer. If a woman is known to have an increased risk, breast MRIs can be performed in addition to mammograms. These would alternate every six months, and can sometimes begin as early as age 25, depending on the gene involved. Surveillance techniques have evolved over time, and continue to progress with the addition of 3D mammograms and Tomosynthesis.

Even if no genetic-cancer risk is found, if a woman has several close relatives diagnosed with breast cancer, she can see a genetic counselor for a personalized risk assessment to determine whether she is eligible for beginning breast MRIs at a younger age as well. This can mean up to 15 additional years of surveillance, at double the frequency, when compared to the surveillance schedule of your average woman.

Surgery: If a woman is found to carry a mutation in a gene with a very high risk for breast cancer, she might consider a surgical option like a “risk-reducing bilateral mastectomy.” “Risk-reducing” means the surgery doesn’t eliminate the risk for breast cancer, but greatly reduces it; “bilateral” means that both breasts are removed; and “mastectomy” means the breast tissue is removed.

There are reconstruction options that can accompany this type of surgery as well. Studies have shown that a bilateral mastectomy can reduce a woman’s risk of developing breast cancer by over 95 percent. Hollywood actress Angelina Jolie made headlines in 2013 when she publically discussed her bilateral mastectomy after discovering she harbored a BRCA1 mutation.

Medication: Some physicians may recommend medication to further reduce a woman’s risk of breast cancer. This is most often in the form of a chemoprevention pill like Tamoxifen.

Other cancers: Each gene that is associated with breast cancer also is associated with at least one other type of cancer. Some of cancers, such as colon cancer, are easily monitored for. Others, such as ovarian cancer, may come with a recommended surgery. And still others, such as pancreatic cancer, have limited recommendations.

Each unique genetic result, combined with each unique family history, can give you a clear picture of your genetic risk for developing cancer, as well as an individualized care plan to stop that cancer in its tracks.

 

Nicole Wood, MS, CGC, is the only licensed and board-certified genetic counselor serving Sarasota County and its surrounding communities. Specialty trained in oncology genetic counseling, Wood works closely with the multidisciplinary Genetic Counseling and Education team at Sarasota Memorial Hospital to provide expertise for patients’ clinical care. She contributes regular blog posts on topics related to genetic testing, counseling and hereditary cancer syndromes.  


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Posted: May 11, 2018,
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Author: Muss
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