Published: Thursday, May 03, 2007
- Hereditary breast cancer
- Features that may suggest an increased risk of a BRCA1 or BRCA2 mutation
- Genetic counselling and genetic testing
- Services offered through the BCCA Hereditary Cancer Program (HCP)
- Process for determining if a patient has hereditary breast cancer
- Special issues concerning genetic counselling and genetic testing
- Screening and monitoring recommendations for BRCA1 or 2 mutations
- Role of tamoxifen in chemoprevention of breast cancer
- Role of prophylactic mastectomy and/or prophylactic oopherectomy in risk reduction for BRCA1 or BRCA2 gene mutations
- Resources for patients concerned about hereditary breast cancer
1. Hereditary breast cancer
Approximately 5-10% of breast cancers are due to an inherited genetic mutation. BRCA1 and BRCA2 were the first two "breast cancer genes" to be identified. BRCA1 is located on chromosome 17 and BRCA2 on chromosome 13. Both are very large genes (thousands of base-pairs in length) and are described as tumour suppressor genes; loss of their normal function conveys an increased risk of breast and ovarian cancer.1
For women who have inherited a mutation in either BRCA1 or BRCA2, the lifetime risk of developing breast cancer is approximately 40-85%. The lifetime risk of developing ovarian cancer is 20-50% for BRCA1 carriers and lower for BRCA2 carriers. Males who carry BRCA1 mutations may have a slightly increased risk of prostate and colon cancer though not at younger ages. Males with BRCA2 mutations have an increased risk of breast cancer (from 0.1% to 6%).2
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2. Features that may suggest an increased risk of a BRCA1 or BRCA2 mutation
See Hereditary Breast and/or Ovarian Cancer to read the BC Cancer Agency Hereditary Cancer Program referral criteria.
3. Genetic counselling and genetic testing
Read about genetic counselling and genetic testing through the Hereditary Cancer Program.
4. Services offered through the BCCA Hereditary Cancer Program (HCP)
Genetic counselling and genetic testing are available through the BC Cancer Agency's Hereditary Cancer Program (HCP), which is based in Vancouver. Services for people who live on Vancouver Island are provided through the Medical Genetics Clinic at the Victoria General Hospital. Genetic counselling appointments are available in Vancouver, Surrey, Kelowna, Victoria, Nanaimo, Courtenay and Campbell River. Genetic counselling is now also available by videoconference in some B.C. communities. Please call 1.800.663.3333 local 2198 to determine availability in your community.
Read about the program components of the Hereditary Cancer Program.
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5. Process for determining if a patient has hereditary breast cancer
Patients who are considered high risk for inherited cancer can be referred to the Hereditary Cancer Program (HCP) in Vancouver or Victoria. Upon referral, services such as genetic counselling, risk assessment, education and surveillance recommendations are available to individuals and families.
Please note:
- Referrals may be made for individuals with or without a personal diagnosis of cancer
- A family history will be assessed by the HCP to evaluate whether a genetic consultation is indicated
- Genetic testing may or may not be offered in the course of a genetics consultation
Referrals can be made by calling the HCP in Vancouver at 604.877.6000 local 2198 or toll free at 1.800.663.3333 local 2198; or the Medical Genetics Clinic in Victoria at 250.727.4461 or toll free at 1.800.670.3322. Referral information and family history forms are available from the BC Cancer Agency Hereditary Cancer Program section of this website.
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6. Special issues concerning genetic counselling and genetic testing
Learn about the special issues concerning the psychological, family, legal, and insurance impacts of genetic testing.
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7. Screening and monitoring recommendations for BRCA1 and 2 mutations
Learn about the clinical management of patients who meet the criteria for the Hereditary Cancer Program's High-Risk Surveillance Clinic.
8. Role of tamoxifen in chemoprevention of breast cancer
- For women at low or normal risk of breast cancer (Gail risk assessment index < 1.66% at five years), there is fair evidence to recommend against the use of tamoxifen to reduce the risk of breast cancer
- For women at higher risk of breast cancer (Gail index > 1.66% at five years), evidence supports counselling women on the potential benefits and harms of breast cancer prevention with tamoxifen. The cutoff for defining high risk is arbitrary, but the National Surgical Adjuvant Breast and Bowel Project P-1 Study included women with a five-year projected risk of at least 1.66% according to the Gail index, and the average risk of patients entered in the trial was 3.2%.
Examples of high-risk clinical situations are two first-degree relatives with breast cancer, a history of lobular carcinoma in situ or a history of atypical hyperplasia. As the risk of breast cancer increases above 5% and the benefits outweigh the harms, a woman may choose to take tamoxifen. The duration of tamoxifen use in such situations is five years based on the results from trials of tamoxifen involving women with early breast cancer. If a woman raises concerns or has already been evaluated and is calculated to be at high risk, then individuals experienced and skilled in counselling may discuss the potential benefits and harms of tamoxifen use.
Important additional issues:
- Prevention of breast cancer with raloxifene: Current evidence does not support recommending chemoprevention of breast cancer with raloxifene outside of a clinical trial setting
- Screening using the Gail risk assessment index: This index was the main eligibility criterion for enrolling women in the one study that showed potential benefit from chemoprevention. However, it has not been evaluated for use as a routine screening or case-finding instrument; validation of the index is required. Overall, current evidence does not support a shift to its routine use in physicians’ offices for screening or case finding. However, when a woman or her physician is concerned about the woman’s increased risk of breast cancer, the index can be a useful tool in deciding whether to pursue an in-depth discussion of the potential benefits and harms of chemoprevention. Hence, the approach to identifying women at higher risk who warrant counselling and shared decision-making will vary across practices. (The risk assessment index is available online at http://bcra.nci.nih.gov/brc/). 3
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9. Role of prophylactic mastectomy and/or prophylactic oopherectomy in risk reduction for BRCA1 or BRCA2 gene mutations
Currently, there are no specific recommendations for or against prophylactic mastectomy. This is usually a personal decision. Prophylactic mastectomies will decrease the risk of developing cancer by 99%. The implications of disturbance in body image, impact on sexuality, and risks and morbidity of surgery need to be discussed fully, and considered as part of the decision-making process.
Because no screening tests have been found to be effective in the early detection of ovarian cancer, the HCP recommends that women who are confirmed to carry a BRCA1 or BRCA2 gene mutation have bilateral salpingo-oopherectomy when childbearing is complete, usually by their late 30s or early 40s.4
10. Resources for patients who are concerned about hereditary breast cancer
- Hereditary Cancer: Is My Family at Risk? - Printable patient information in the BCCA Hereditary Cancer Program section
- Hereditary Breast Cancer - Patient information tool available online or in booklet/ audiotape format from the Canadian Cancer Society
- A decision guide to assist women contemplating prophylactic mastectomy is available through the BCCA Hereditary Cancer Program 1.800.663.3333 Local 2198.
The following websites may also be of interest:
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REFERENCES
1. BC Cancer Agency (http://www.bccancer.bc.ca). Vancouver (BC): 2006. (cited Oct 25, 2006). Available from: http://www.bccancer.bc.ca/HPI/CancerManagementGuidelines/HereditaryCancerProgram/GeneticTesting.htm
2. BC Cancer Agency (http://www.bccancer.bc.ca). Vancouver (BC): 2006. (cited Oct 25, 2006). Available from: http://www.bccancer.bc.ca/HPI/CancerManagementGuidelines/HereditaryCancerProgram/FamilialCancerSyndromesAutosomalDominantDisorders.htm
3. Clinical practice guidelines for the care and treatment of breast cancer, Guideline 12: Chemoprevention of breast cancer, June 12, 2001, © 2006 CMA Media Inc. or its licensors.
4. BC Cancer Agency (http://www.bccancer.bc.ca). Vancouver (BC): 2006. (cited Oct 25, 2006). Available from: http://www.bccancer.bc.ca/HPI/CancerManagementGuidelines/HereditaryCancerProgram/ClinicalManagement.htm