Understanding Hereditary Breast and Ovarian Cancer. Maritime Hereditary Cancer Service

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1 Understanding Hereditary Breast and Ovarian Cancer Maritime Hereditary Cancer Service

2 General Information Cancer is very common. About one in three (33%) people are diagnosed with some form of cancer during their lifetime. Approximately 1 in every 9 women in Canada (11%) will be diagnosed with breast cancer during their lifetime, and about 1 in 70 (1.4%) women will be diagnosed with ovarian cancer. Cancer occurs when the cells in our body grow and divide in an uncontrolled way. This happens when the body s normal control of cell growth and division is not working properly, because of changes that have occurred in our hereditary information (our genes). Our genes are the basic units of hereditary information. They are our body s instructions for growth, development and day-to-day functioning. Genes come in pairs; we inherit one copy of each gene from each parent. Changes (known as mutations) can occur in our genes, which can cause them to not work properly. Sometimes these mutations happen over the course of our lifetime, but we can be born with mutations as well. It is thought that everyone is born with a few gene mutations, most of which never cause any medical concern. 2

3 Percentage of Hereditary vs. Sporadic Cancer All cancer is caused in part by changes in our genetic material, but the vast majority of these mutations occur because of environmental exposures, lifestyle factors, the aging process, or random chance. Most cancers are not hereditary. Only about 5-10% of breast and ovarian cancer is thought to be hereditary, or due to a mutation that is passed through the generations in a family. This means that 90-95% of all cancers are not hereditary. 1. Percentage of Hereditary vs. Sporadic Cancer 2. Hereditary Cancer 5 to 10% 3. Sporadic Cancer 3

4 Hereditary Cancer Mutations in at least two genes, BRCA1 and BRCA2, are associated with hereditary breast and ovarian cancer. An individual born with one of these mutations has inherited a predisposition to developing cancer. In other words, compared to the general population, they have a higher chance of developing cancer, most commonly breast cancer (50-85% lifetime chance vs. 11%) and ovarian cancer (15-40% lifetime chance vs. 1.4%). Hereditary breast and ovarian cancer is inherited in a dominant manner. This is illustrated in the following diagram. When one parent carries a BRCA mutation, there is a 1 in 2 (50%) chance of passing down the copy of the gene with the mutation to each child ( a ). There is also a 1 in 2 (50%) chance of passing down the working copy of the gene ( A ). It is important to remember that it is a predisposition to cancer that is inherited, not cancer itself. It is possible that an individual with a BRCA mutation never develops cancer. 4

5 1. general population risk of cancer 2. increased risk of cancer 3. increased risk of cancer 4. general population risk of cancer 5

6 Genetic Testing for the BRCA1 and BRCA2 genes Genetic testing is available to individuals who have had breast and/or ovarian cancer and whose families meet specific guidelines. These guidelines exist so that we can offer genetic testing to the families who are most likely to benefit from this testing. The family history you described is most consistent with hereditary breast and ovarian cancer syndrome, and you were offered genetic testing of the BRCA1 and BRCA2 genes. Although available, genetic testing is completely voluntary. There are a number of things to consider prior to having genetic testing. It is important to think about how you will use this information. Learning that you have a BRCA1/2 gene mutation is not a diagnosis of cancer; it cannot tell you when, if, or what kind of cancer you may develop. However, results may empower you to make informed decisions about your health and may allow other family members to do the same. Below are some possible benefits and limitations of genetic testing for BRCA1/2. We are still learning about how the genetic testing process affects people s lives. 6

7 Results may provide helpful information for family members, and may explain the family history of cancer. Results may help some people make medical and lifestyle decisions, including screening and surgery options (risk-reducing strategies). The available cancer screening may have false positive and false negative rates (i.e. detecting a problem when there is not one and/or missing a problem when one exists). Results may reduce anxiety for some people, and may increase anxiety for others. As our genes are shared with our relatives, results may have an impact, either good or bad, on family relationships. Some family members may have different feelings about genetic test information and sharing that information. Although unlikely, you may experience discrimination with employers or insurance companies should they learn you are a mutation carrier. If a mutation is not found, families may perceive this as a false sense of security regarding their chances to develop cancer. 7

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9 The decision about whether or not to have genetic testing is a personal one. It is important to make the decision that is right for you, at the right time in your life. One of the goals of genetic counselling is to provide support and information to individuals making this decision. 9

10 Possible Results of Genetic Testing 1. Testing identifies a mutation: This result would provide an explanation for the pattern of cancer in your family. It is associated with an increased chance of breast and ovarian cancer, and specific high-risk screening and/or management recommendations would be made for yourself and/or your family members. Genetic testing for this specific mutation would be available to all interested adult family members. 2. Testing does not identify a mutation: This result would not provide a genetic explanation for the cancer in your family. Possible reasons for this result include: a) The cases of cancer in your family may not be hereditary, b) there may be a mutation that we are unable to detect, in either BRCA1, BRCA2, or another cancer susceptibility gene that has not been tested, or c) a genetic predisposition may be in your family but you do not appear to have it. 3. Testing reveals a genetic change of unknown significance: This would not provide an explanation for the cancer in your family, and we would discuss how to further clarify this result. 10

11 If testing reveals no mutation (possibility 2 or 3, above), genetic testing would most likely not be available for other family members. In this situation, the genetic assessment and screening recommendations would be based on family history alone. Regardless of the outcome of genetic testing, once a family member has experienced cancer, others in the family are at an increased risk to develop cancer. 11

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13 We hope the information presented here has been helpful. It is based on our current understanding of hereditary breast and ovarian cancer. As knowledge in this area is evolving rapidly, we encourage your family to remain in touch with our clinic to learn about any new information and inform us of any new diagnoses of cancer in your family. For More Information: Maritime Hereditary Cancer Service IWK Health Centre PO Box 9700, 5850/5980 University Avenue Halifax, NS B3K 6R8 Phone: (902) or toll free , extension 8754 Fax: (902) PL-0712 Last Update: 11/10 Next Review: January,