Cancer Clues in the Genome

Nearly 30 years ago, Mary-Claire King, PhD, made a discovery that would revolutionize the way the scientific community thought about inherited disease: She found a gene on chromosome 17 that was linked to countless cases of breast and ovarian cancer. The gene would later be named BRCA1, and it would be joined by BRCA2 a year later. We now know that people with a BRCA1 or 2 mutation are at a higher risk of developing certain cancers, and physicians and patients are using this information for prevention and early diagnosis.

Ever since Dr. King’s discovery, researchers have continued to search for genetic links, and a study published in JAMA Oncology in August provides new insight into those efforts.


Low-Dose Aspirin May Protect Against Ovarian Cancer

A study published in JAMA Oncology in October found that taking a low dose (100 milligrams or less) of aspirin every day may reduce the risk of ovarian cancer by 23 percent. Taking a standard dose (325 mg) did not have the same effect, and women who regularly take nonsteroidal anti-inflammatory drugs (NSAIDs) appeared to have a higher risk of developing ovarian cancer. Similar findings were reported earlier this year in the Journal of the National Cancer Institute. Other recently published studies, however, found that low-dose aspirin may pose a risk of harm. See the news item on page two for more information on those findings.

New Genes Linked to Breast and Ovarian Cancer. The researchers from Ambry Genetics looked at the genes of more than 11,000 people with breast cancer (including 123 men), ovarian cancer, or both, and nearly 4,000 healthy controls. They confirmed that two previously identified additional genes are associated with a higher risk of breast cancer (PALB2, CHEK2), and two are associated with an increased risk of ovarian cancer (RAD51C, TP53). They also reported that two new genes, ATM and MSH6, should now be considered possible predisposition genes for both diseases. They did not find a relationship between the BRIP1, RAD51C, RAD51D, MSH2, or PMS2 genes and a higher risk of breast cancer, despite other research that suggested such a link.

People Don’t Know They’re at Risk. While scientists know more than ever about the genetic underpinnings of disease, patients are still often in the dark. More than 80 percent of people who are carrying a high-risk gene are unaware of it, according to a study published in September in JAMA Network Open. Most people discover their genetic risk only when they or a family member are diagnosed with cancer. That’s a missed opportunity for early diagnosis and prevention, noted lead author Michael Murray, MD, FACMG, FACP, in a Yale University press release.

What You Should Know. If you have a family history of breast or ovarian cancer, genetic counseling and possibly testing may provide insight into your own level of risk. Genetic testing is not recommended for people who do not have a family history of these diseases.

If you test positive for a genetic mutation that is associated with breast or ovarian cancer, it does not mean you will develop cancer, only that you are at a higher risk. Risk-reduction strategies, such as more frequent screening, may be recommended. Similarly, testing negative for these genes does not mean that you will not develop breast or ovarian cancer, as they account for only a portion of breast and ovarian cancer cases.


A Significant Step Forward

“Approximately 3 to 5 percent of breast cancers and 16 to 18 percent of ovarian cancers are caused by inherited mutations in the genes BRCA1 or BRCA2. Over the last decade, researchers have identified additional genes, such as PALB2 and RAD51C, that are also associated with increased risk of breast or ovarian cancer. The present study is a significant step forward as it suggests that two new genes, MSH6 and ATM, may also be associated with increased risks of these cancers. This is important information as individuals identified as having a mutation in one of these genes can take advantage of proven strategies to reduce their risk. If you do have a family history of breast or ovarian cancer, genetic counseling and, in appropriate cases, genetic testing can help clarify your risks and strategies are best suited to reduce those risks.”

Noah D. Kauff, MD
Director, Clinical Cancer Genetics,
Duke Cancer Institute,
Duke University Health System

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