Breast Health |
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Genetic Testing For Breast And Ovarian Cancer RiskLearning More, Making Informed DecisionsWith increasingly sophisticated scientific tools, physicians and geneticists are able to tell women more information than ever before about the degree to which they may be affected by inherited syndromes that put them at greater risk for developing certain kinds of cancers.
Only 5-7% of breast and 10-15% of ovarian cancers are attributed to inherited syndromes. Most breast and ovarian cancers occur due to non-inherited factors (for instance, we know that smoking has been linked to increased risk of breast cancer in women). “Genetic testing can be a powerful tool, but this testing is appropriate only for a small proportion of women with breast or ovarian cancers”, says Susan Jones, cancer genetics counselor at the University of Virginia NCI Clinical Cancer Center. Genetic testing, or analysis of the DNA of a specific gene, may reveal whether risk for breast or ovarian cancer is inherited in a family. How do genes affect cancer? Cancers develop due to alterations (mutations) in genes. However, only a small percentage of cancers involve inherited mutations that are passed from generation to generation. The majority of cancers can be attributed to "acquired" mutations. Acquired means that the mutations occur only in the tissue that is affected by cancer and are not present in all cells of the body. Acquired mutations are not inherited and are not passed down to children. In fact, all people carry altered forms of some genes, according to the National Cancer Institute (NCI). Some alterations can increase risk for certain illnesses such as cancer. In recent years, gene alterations have been found in some families with a history of breast cancer. Some women in these families also have had ovarian cancer. Genetics as part of comprehensive care As one of only a few dedicated cancer genetics counselors in Virginia, UVa’s Susan Jones works to ensure that patients and doctors understand when and how genetic testing is used. “It is important for women to understand that genetic testing doesn’t happen in a vacuum - it is only one small part of her coordinated medical care. While the test itself requires only a blood sample, careful consideration needs to be given to whether a woman is a candidate for testing, and how the information will be used to direct her care”. Women with a strong family history of breast or ovarian cancer, or who otherwise feel they may have an inherited cancer syndrome, should first talk to their primary care physician or cancer specialist. If a woman and her doctor agree that genetic testing is warranted, a referral can be made to a special cancer genetics service. UVa Health System’s Cancer Genetics Clinic has one of only a few dedicated cancer genetics counselors in Virginia, and is based in UVa’s NCI-designated Clinical Cancer Center. What is involved in cancer genetics services? Jones describes three components in genetics services: § Evaluation of the personal and family history. Jones explains: “Before a woman is seen, we obtain a full medical and family history to first determine the likelihood that the patient has an inherited cancer syndrome, and if so, which of several syndromes this might be.” § Consultation. The conclusions of the evaluation are shared with the patient. This involves reviewing medical and genetic information. The genetic counselor will also discuss with the patient what her feelings are about being tested, how she intends to use the information obtained through testing, and what she thinks the personal and family impact might be of the test results. § DNA testing. If the patient wishes to proceed, a blood test is done for the particular gene(s) suspected of being altered in the family. Results of the DNA analysis are shared with the patient at a follow-up clinic visit. Some women undergo testing to determine if they have an inherited syndrome so that they can take action to help lower the chance that cancer might occur. Others may have been diagnosed with cancer and are interested in determining whether they may have passed a genetic alteration to children. “For most women, it’s a combination of both concerns,” says Jones. “That’s why the test itself is only a small part of what we do.” The results of genetic evaluation and/or testing are then shared with the patient’s physician, and can be critical in developing a tailored plan of care. “Ultimately, cancer genetics services are about allowing women to make informed decisions,” says Jones. If a woman is at increased risk for breast or ovarian cancer, she can make choices that may help reduce her risk of getting cancer or help find cancer early. Advantages of testing The National Cancer Institute (NCI) states that there can be benefits to genetic testing, whether a person receives a positive or a negative result. A positive test result can bring relief from uncertainty and allow people to make informed decisions about their future, including taking steps to reduce cancer risk. The potential benefits of a negative result include a sense of relief and elimination of the need for special preventive checkups, tests, or surgeries. How does genetic testing work? Genetic testing for breast and ovarian cancer risk involves looking for alterations in genes such as BRCA1 and BRCA2. Although the laboratory analysis is quite complex, only a blood sample is needed. Hereditary Breast and Ovarian Cancer (HBOC) Hereditary breast and ovarian cancer (HBOC) is the most common inherited syndrome that has been identified with an increased risk of breast and ovarian cancer. HBOC may be characterized by the following features in a family:
Other factors that increase the chance that a family has HBOC include a personal/family history of male breast cancer and Ashkenazi Jewish ancestry. However, Ms. Jones emphasizes that family histories are not perfect tools for knowing if HBOC is present. BRCA1 and BRCA2 Genes In 1990, DNA linkage studies on large families with the above characteristics identified the first gene associated with breast cancer. Scientists named this gene “breast cancer 1” or BRCA1 (pronounced brak-uh). BRCA1 is located on chromosome 17. Mutations in the gene are transmitted in an autosomal dominant pattern. In autosomal dominant inheritance, the mutation is carried and transmitted equally by women and men. This means that a mutation for breast cancer risk can be carried by and transmitted by men. Since it was clear that not all breast cancer families were linked to BRCA1, studies continued and in 1994, scientists discovered another gene (similar to BRCA1), and named it BRCA2. BRCA2 is located on chromosome 13. Mutations in this gene are also transmitted in an autosomal dominant pattern in a family. Both BRCA1 and BRCA2 are tumor suppressor genes, whose normal function is to control cell growth and cell death. Everyone has two BRCA1 (one on each chromosome #17) and two BRCA2 genes (one on each chromosome #13). When a person has one altered or mutated copy of either the BRCA1 or BRCA2 gene, the risk for various types of cancer increases. The following are facts about BRCA1 mutations:
The following are facts on BRCA2 mutations:
Online Resources(Our Organization is not responsible for the content of Internet sites.) American Society for Clinical Oncology Centers for Disease Control and Prevention (CDC) National Institutes of Health (NIH) |
April 2004What is genetic testing? Genetics as part of comprehensive careWhat is involved in cancer genetics services? Online ResourcesStatistics for Breast and Ovarian CancerAccording to estimates of lifetime risk from the National Cancer Institute (NCI), about 13 percent (132 out of 1,000 individuals) of women in the general population will develop breast cancer, compared with estimates of 36 to 85 percent (360 to 850 out of 1,000) of women with an altered BRCA1 or BRCA2 gene. In other words, women with an altered BRCA1 or BRCA2 gene are three to seven times more likely to develop breast cancer than women without alterations in those genes. Lifetime risk estimates of ovarian cancer for women in the general population indicate that 1.7 percent (17 out of 1,000) will get ovarian cancer, compared with 16 percent to 60 percent (160 to 600 out of 1,000) of women with an altered BRCA1 or BRCA2 gene. Women with an inherited alteration in one of these genes have an increased risk of developing these cancers at a young age (before menopause), and often have multiple close family members with the disease. Men with an altered BRCA1 or BRCA2 gene also have an increased risk of breast cancer (primarily if the alteration is in BRCA2), and possibly prostate cancer. Testing Pluses and MinusesThe National Cancer Institute (NCI) suggests that genetic testing may help a woman:
There are also disadvantages to testing, according to the NCI:
A woman will need to decide what the advantages and disadvantages of testing are for her. What is right for one person is not always right for another. Always consult your physician for more information. Questions to Ask About Genetic TestingIf a woman is considering genetic testing, she should discuss this with her physician or genetic counselor. The following questions are provided by the National Cancer Institute (NCI):
Always consult your physician for more information. |
But information alone isn’t always useful. In fact, genetic testing is only truly helpful when understood in the context of each unique woman’s life, family circumstances, and medical and family history.