Understanding Hereditary Breast & Ovarian Cancer – the BRCA genes understanding hereditary breast & ovarian cancer – the brca genes 3 Contents Introduction Introduction ___________________________________________________________ 3 The purpose of this booklet is to review the information How are cancer & genes related? _________________________________________ 4 about hereditary breast and ovarian cancer as discussed in What is known about hereditary cancer? ___________________________________ 5 a genetic counselling session. You may also wish to use this Is my family at risk? _____________________________________________________ 6 booklet to help you share information with other family members. The BRCA1 and BRCA2 genes _____________________________________________ 7 What happens if there is a mutation in a BRCA gene? _________________________ 7 This booklet was prepared by staff of the Hereditary Cancer What happens if a person inherits a BRCA gene mutation? ____________________ 8 Program, based on information that was current at the time What are the risks for the children of a BRCA gene mutation carrier? ___________ 9 of printing. What is the risk of cancer for a BRCA gene mutation carrier? __________________10 What is genetic testing? _________________________________________________ 11 Words that may be new to you are highlighted and are Who can have BRCA genetic testing? ______________________________________ 11 defined in the Glossary on page 28. How is BRCA genetic testing done? ________________________________________12 Results of BRCA genetic testing ___________________________________________13 Cancer screening _______________________________________________________14 What about surgery to reduce cancer risks? ________________________________16 Taking care of your health _______________________________________________18 Issues to consider ______________________________________________________19 What are some pros and cons of genetic testing? ____________________________21 How to contact the Hereditary Cancer Program ____________________________ 22 Resources ____________________________________________________________ 23 - Peer Support Groups ______________________________________________ 23 - Decision Guides __________________________________________________ 24 - Books __________________________________________________________ 24 - Videos __________________________________________________________ 25 Acknowledgments - Websites ________________________________________________________ 26 We are grateful to the many people who Glossary _____________________________________________________________ 28 provided such valuable feedback as this booklet developed, and to the BC Cancer Appendix: What are DNA, chromosomes and genes? ________________________ 30 Agency Multimedia Services Department Notes_________________________________________________________________31 for design, layout and illustration. 4 understanding hereditary breast & ovarian cancer – the brca genes understanding hereditary breast & ovarian cancer – the brca genes 5 How are cancer & genes related? What is known about hereditary cancer? Each gene has a specific function in the body. Some genes control cell About 5-10% of all cancer cases (less than 1 in 10) are thought to be division. When mutations occur in these genes, a cell may begin to due to an inherited gene mutation. That means that most cancer is not divide without control. Cells that divide when they are not supposed hereditary. to may eventually become a cancer. See Appendix on page 30 for more information about genes, chromosomes and DNA. 10 people with cancer All cancer is genetic, most is not hereditary All cancers are the result of gene mutations. Mutations may be caused Hereditary cancer by aging, exposure to chemicals, radiation, hormones or other factors in the body and the environment. Over time, a number of mutations may occur in a single cell, allowing it to divide and grow in a way that Research has found some of the genes that help to explain specific becomes a cancer. This usually takes many years, and explains why most patterns of hereditary cancer. Other genes will be identified in the future. cancers occur at a later age in life. Because people are not born with these acquired gene mutations, they cannot pass them on to their children. A small number of cancers are hereditary. This means that they are related to a specific gene mutation that is passed down (inherited) in a family. A person who is born with a mutation has it in every cell in his/her body, including some of the eggs or sperm. This means it may be passed down to the next generation. Individuals who inherit such gene mutations have a higher risk of developing certain forms of cancer compared to the general population. Inherited gene mutations help to explain why in some families, we see more people than expected with certain kinds of cancer. Hereditary 5 - 10% Familial 20 - 25% Sporadic 70 - 75% 6 understanding hereditary breast & ovarian cancer – the brca genes understanding hereditary breast & ovarian cancer – the brca genes 7 Is my family at risk? The BRCA1 and BRCA2 genes The history of cancer in your close relatives is a clue to the chances of BRCA is an abbreviation for breast cancer. BRCA1 and BRCA2 were the hereditary breast/ovarian cancer. Close relatives include your: children, first two genes discovered to be responsible for some hereditary breast brothers, sisters, parents, aunts, uncles, grandchildren, and grandparents, cancer and some hereditary ovarian cancer. on one side of the family. History of cancer in cousins and more distant relatives may also be important. An inherited mutation in the BRCA1 or BRCA2 genes is more likely if at least 1 of the following features can be confirmed in your family: ☐ A woman with breast cancer diagnosed at age 35 or younger ☐ A woman with ovarian cancer ☐ A woman with breast cancer and ovarian cancer Everyone is born with two copies of BRCA1 and two copies of BRCA2, ☐ A woman with 2 or more separate breast cancers, if the 1st diagnosis one copy of each gene from their mother and one copy of each gene from was at age 50 or younger their father. These genes are found in every cell of the body, but are most ☐ A man with breast cancer and a close relative with breast cancer or important in breast cells and ovary cells. Because BRCA1 and BRCA2 ovarian cancer work in the same way, we will refer to them as BRCA genes in most of this booklet. Where there are specific differences, the genes will be ☐ A woman with breast cancer and a close relative with ovarian cancer described separately. ☐ 2 closely related women with breast cancer, both diagnosed at age 50 or younger A BRCA gene is the “code” to make a BRCA protein. This protein’s ☐ 3 closely related women with breast cancer, at least one of whom was function is to control the division of cells in the breasts and ovaries. The diagnosed at age 50 or younger protein acts like a traffic signal; it allows breast cells to divide during puberty (green light), and stops them from dividing at other times (red ☐ Ashkenazi (European) Jewish heritage and some family history of light). breast cancer or ovarian cancer Notes: What happens if there is a mutation in a BRCA gene? Breast cancer – does not include LCIS (lobular carcinoma in situ) Because we have two copies of every gene, a mutation in one copy of a Ovarian cancer – includes fallopian tube and primary peritoneal cancers. BRCA gene in a breast or ovary cell does not cause a problem; the other Pathology reports are needed to confirm the type of ovarian cancer copy can still produce the protein to control cell growth. A mutation because some of the less common types are not associated with inherited must occur in both copies of the same BRCA gene in the same cell for the BRCA1/2 mutations. control to be lost and a cancer to develop. 8 understanding hereditary breast & ovarian cancer – the brca genes understanding hereditary breast & ovarian cancer – the brca genes 9 What happens if a person inherits a BRCA gene What are the risks for the children of a BRCA gene mutation? mutation carrier? This person is born with a mutation in one copy of a BRCA gene Remember that we inherit one copy of each of our genes from each and this mutation is present in every cell of the body. The other copy of parent, and we pass on one copy of each of our genes to our children. This that gene is normal and is able to “do its job”. This person is a BRCA gene means that every time a carrier has a child, either the normal copy of the mutation carrier. gene or the gene with the mutation can be passed on. As shown below, each child has a 50/50 chance to inherit the gene mutation. As a person ages, DNA mutations occur by chance, in different genes, in different cells. A woman who is born with 2 normal copies of the BRCA Non-carrier parent Carrier parent genes in every cell has to acquire a mutation in both copies of the same BRCA gene in the same breast or ovary cell for a cancer to develop. This is what happens in sporadic cancer. Sporadic Cancer Cancer Hereditary Cancer Non-carrier child Carrier child Cancer Normal gene Gene mutation Non-inherited mutation Inherited mutation A child who inherits 2 normal A child who inherits the mutation If a mutation occurs by chance in the normal copy of a BRCA gene in a copies is not a carrier, does not is a carrier, and has an increased breast or ovary cell when a woman is a BRCA mutation carrier, the cell have increased risk for cancer, and risk of being diagnosed with no longer has a working copy of that gene. The normal BRCA protein cannot pass the mutation on to certain types of cancer over his/ his/her children. her lifetime (see page 10). will not be made and a cancer may develop. That helps to explain why a woman who inherits a BRCA gene mutation is much more likely to be diagnosed with breast cancer or ovarian cancer than is a non-carrier. The way we inherit genes explains why it is important to look at the Hereditary cancer is also more likely to be at a younger age than the same history of cancer on both sides of a family.