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Genetic Testing for Breast Cancer

  • BRCA Gene Mutations

  • In November of 2008, Corrine* was 40-years-old and getting ready to welcome her first child into the world. Near the end of her pregnancy, she received unnerving news. Her older sister was diagnosed with an aggressive form of breast cancer. It had spread.

    The mother of two underwent a double mastectomy, radiation, chemotherapy and reconstruction. “It was an arduous 18-month battle for her,” said Corrine. After the diagnosis, Corrine’s sister had a BRCA gene test—a blood test that uses DNA analysis to identify changes in either one of two breast cancer susceptibility genes — known as BRCA1 and BRCA2. Both belong to a class of genes known as tumor suppressors. In normal cells, BRCA1 and BRCA2 help prevent cancer by making proteins that help keep the cells from growing abnormally. Mutation of these genes has been linked to the development of hereditary breast and ovarian cancer.

    “My sister had the BRCA1 mutation. I was completely shocked. Breast cancer didn’t run in our family,” said Corrine. “It was a lot to deal with in a very short period of time. I eventually wanted to know if I had the mutation too, but at the time I just needed to be in the moment so I could get through the rest of my pregnancy.”

    After the New Year, Corrine gave birth to a healthy baby boy. A business woman and single mom, she went back to work after her maternity leave ended. Breastfeeding and swamped with new responsibilities, she waited more than a year to go through genetic testing.

    “I guess I wasn’t ready to hear the news yet,” she said.

  • Genetic Testing

  • The results of a genetic test can often confirm or rule out a suspected genetic condition or help determine a person's chance of developing or passing on a genetic disorder.

    “Genetic testing involves analyzing complex information and navigating emotional topics. We are here to help people through the whole process,” said Alexandria Yonker, a genetic counselor at CPMC’s Bryan Hemming Cancer Care Center in San Francisco. “Breast cancer is common, so the majority of the patients I see are concerned about BRCA mutations. Since they are so rare, I often deliver good news. I am able to provide people with a great sense of relief, which is the best part of my job.”

    Because BRCA mutations are often detected in women who are relatively young, Alexandria’s job also entails difficult conversations.

    “They have their whole lives ahead of them, so the decisions can be more difficult. But I can let them know about surveillance and prevention strategies,” she said. “Together, we take it one step, one emotion and one decision at a time.”

  • Risk and Prevention

  • For women who have inherited a mutated BRCA gene, the chances of developing breast cancer in their lifetime may be as high as 80 percent, according to the American Cancer Society. There are ways to reduce a carrier’s risk. Those measures are individualized, based on the person’s age, family plans, medical history and personal experience.

    “Carrying the mutation does not mean a person will absolutely get cancer, so some choose watchful waiting, meaning they undergo routine imaging procedures and breast exams,” said Alexandria. “Many others opt for preventive surgery, especially if they have already had cancer or a loved one who suffered or died from the disease. Some studies show that half of women with BRCA mutations elect to have risk-reducing mastectomy and the majority undergo surgery to remove their ovaries.”

    Fortunately, BRCA mutations are rare, occurring in about one in 800 people. They are found more often in individuals of Ashkenazi Jewish decent, but can occur in any racial or ethnic group. The gene defects are responsible for approximately 5 to 10 percent of breast cancers and about 10 to 15 percent of ovarian cancers, according to the National Cancer Institute.

  • Corrine’s Results

  • When Corrine’s son was about 18-months-old, she sought genetic counseling services at CPMC to find out if she too carried the BRCA1 mutation. Testing determined the new mom didn’t have it, but several other members of her family did, including her dad, aunt, cousin and another sister.

    “My sister proceeded with careful screening because of her positive gene test. As a result, she was diagnosed with breast cancer very early before the disease spread,” said Corrine.

    Her sister had a triple negative breast cancer, which is commonly seen among BRCA1 mutation carriers and difficult to treat once it spreads. She had a double-mastectomy, which successfully removed the cancer.

    “I am glad we had the information we did from the genetic testing,” said Corrine. “My sister might not be here if we didn’t know about our family’s genetic predisposition. She was able to make an informed decision while she still had one.”

    *The name of the patient was changed to protect her family’s privacy.

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