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Scientists Identify First Genes Linked to Triple-Negative Breast Cancer

Discovery may lead to earlier diagnoses and better prevention strategies (Image: Mayo Clinic).

Over 266,000 women will be diagnosed with breast cancer in 2018, according to the American Cancer Society, and nearly 41,000 women will die from breast cancer this year. Despite significant advances in diagnosis and treatment made by the medical, scientific and corporate communities, breast cancer remains the most common cancer among women, excluding certain types of skin cancer.

The majority of women with breast cancer have cancer cells that have certain receptors—estrogen receptor, progesterone receptor or human epidermal growth factor receptor 2 (HER2)—that can be targeted with hormone therapy such as tamoxifen (Nolvadex) and HER2 therapy such as trastuzumab (Herceptin). Patients who have triple-negative breast cancer, however, are not treatable with these drugs because their cancer cells lack those three receptors. Triple-negative breast cancer accounts for about 15% of breast cancer among white women and 35% among black women. It’s an aggressive form of cancer that is associated with advanced disease stage and high-grade tumors at diagnosis. Triple-negative breast cancer also has a higher risk of recurrence and poor five-year survival rates relative to other breast cancers.

A new path to early diagnosis

A global team of 29 researchers has, for the first time, identified specific genes associated with an increased risk of developing triple-negative breast cancer. The team was led by Fergus Couch, PhD, a geneticist at the Mayo Clinic’s Department of Laboratory Medicine and Pathology and Department of Health Sciences Research, and its report was published yesterday in the Journal of the National Cancer Institute.

[The video below from the Triple Negative Breast Cancer Foundation is over six years old, but it provides a good overview on this aggressive disease. The age of the video actually serves to emphasize the severity of the disease, the difficulty of diagnosis and the magnitude of the discovery by Dr. Couch and his colleagues.]

Source: Triple Negative Breast Cancer Foundation, 2012.

Dr. Couch and his team performed genetic testing on 10,901 patients with triple-negative breast cancer from two studies. They tested 21 cancer predisposition genes in 8,753 patients and 17 genes in the remaining 2,148 patients. They found that mutations in the BARD1, BRCA1, BRCA2, PALB2 and RAD51D genes were associated with a high risk for triple-negative breast cancer and a greater than 20% lifetime risk for overall breast cancer. Additionally, the team discovered that mutations in the BRIP1 and RAD51C genes—which were previously thought to be associated only with ovarian cancer—were linked to a more moderate risk of triple-negative breast cancer.

According to Dr. Couch, the study “is the first to establish which genes are associated with high lifetime risks of triple-negative breast cancer.” These findings will enable expanded genetic testing to identify women at risk for triple-negative breast cancer and may potentially lead to better prevention strategies. They also may lead to revisions to the National Comprehensive Cancer Network screening guidelines, which currently recommend only BRCA testing when a patient has a family history of breast cancer or is diagnosed at age 60 or younger.

Avichai Scher, writing on the study findings for NBC News, cited comments from Sandra Swain, MD, Medical Director of the Washington Cancer Institute of the Washington Hospital Center and Professor of Medicine at Georgetown University. Dr. Swain, who was not among the study researchers, said, “Triple-negative is hard to treat and has low survival rates, especially in a recurrence. It’s really exciting discovering more and more genes that can help with treatment.”

Scher wrote further that Dr. Swain cautioned that “it’s undetermined who should be screened for the genetic mutations [as] over 30% of the triple negative patients in the study had no family history of breast cancer and other risk factors aren’t well understood. ‘Unless we start testing everyone for these genes, it’s unclear how we can effectively screen for first-time cases,’ Swain said.”

Dr. Couch concluded that women who are identified through testing as having elevated risk of triple-negative breast cancer “can potentially benefit from improved screening, risk management, and cancer prevention strategies. Patients with mutations may also benefit from specific targeted therapeutic strategies.”

We salute Dr. Couch and his global team of scientists who worked on this landmark study at institutions across the US and in Germany, the United Kingdom, Greece and Finland.

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