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Download the PDF here. Download the point of care tool to assist identifying patients most likely to benefit from referral to genetics or the more comprehensive review, the GECKO Messenger containing more on risks, benefits, limitations, screening and management, as well as for the made for practice. Access an an education module with case-based learning here.


Bottom line: Breast cancer is relatively common in the general population (12% lifetime risk) and the majority of cases occur sporadically. About 5-10% of breast cancer is due to an inherited gene change. Mutations in the genes BRCA1 or BRCA2 are the most common cause of hereditary breast and ovarian cancer (HBOC) and BRCA1 and BRCA2 mutation carriers have a significant increased lifetime risk for breast and ovarian cancer in addition to other cancers. Risk-reducing surgeries and, for some women, chemoprevention, can reduce mortality from breast and ovarian cancers in both BRCA1 and BRCA2 carriers. Individuals with family histories of breast or ovarian cancer that are at high risk (generally >10%) to carry a BRCA1 or BRCA2 gene mutation can be offered referral to genetics services for a discussion of the benefits, harms and limitations of genetic testing, while women whose family histories suggest a low risk of carrying a BRCA1 or BRCA2 gene mutation can be reassured and offered screening following provincial guidelines.

Updated April 2016; Under review

What is Hereditary Breast and Ovarian Cancer Syndrome?

Approximately 80% of breast cancer occurs sporadically. About 10-15% of breast cancer is familial (when shared familial risk factors e.g. genes, environment, cause a higher incidence of cancer) and about 5-10% is hereditary (due to a single gene mutation). Harmful mutations in BRCA1 and BRCA2 appear to account for ~30% of high-risk breast cancer families. HBOC is an autosomal dominant cancer predisposition syndrome. Individuals with HBOC have a high risk for breast and ovarian cancers and a moderate risk for other cancers (Table 1). Not all individuals who inherit a mutation in BRCA1 or BRCA2 will develop cancer (reduced penetrance) and the signs and symptoms, type, and age of onset of cancer will vary within families (variable expressivity).

It is estimated that the general population prevalence of pathogenic mutations in the BRCA1 and BRCA2 genes is 1 in 300 to 1 in 500. Founder mutations are observed in individuals of Ashkenazi Jewish ethnicity occurring at an estimated frequency of about 1 in 50.

Who should be offered genetic testing?

These are general guidelines to identify patients at high risk for HBOC. You should consider referring your patient to your local genetics centre or hereditary cancer program for further assessment if s/he has a family or personal history of:

  • Breast cancer diagnosis at a young age (<35-45 years) [both invasive and ductal carcinoma in situ]
  • Ovarian cancer at any age [epithelial]
  • Male breast cancer
  • Multiple primaries in the same individual e.g. bilateral breast cancer (particularly if the diagnosis was before age 50), breast and ovarian cancer
  • Breast cancer diagnosis AND a family history of two or more additional HBOC- related cancers, including breast, ovarian, prostate (Gleason ≥7) and pancreatic cancer
  • High risk ethnicity (Ashkenazi Jewish, Icelandic) and a personal and/or family history of breast, ovarian or pancreatic cancer
  • Triple negative breast cancer diagnosed <age 60

OR if s/he has a personal

  • Probability of 10% or higher to carry a BRCA mutation

Eligibility criteria for genetic testing vary among organizations. In general, criteria are based on clinical features that increase the likelihood of a hereditary cancer susceptibility syndrome.

If possible, testing is first offered to the affected individual in the family at highest risk to carry a mutation in order to maximize the likelihood of detecting a mutation. For example, this might be the youngest individual with breast cancer in a family with multiple cases of breast and ovarian cancer.

See the GECKO point of care tool which can be used in your practice to help identify patients that would benefit from referral to genetics or your local hereditary cancer program.

Click here to find your local general genetics clinic. Including the information above on your referral (e.g. family history, genetic test results, and investigations like iron indices) is a good idea to prevent unnecessary delays due to further clarification needed before an appointment can be booked.

Table 1. Links to provincial breast screening programs below. These and other resources can also be found in Resources for clinicians > Specialized provincial programs.

Province/TerritoryHigh risk breast cancer screening guidelinesBreast cancer screening programAdministrative agency
British Columbia High risk eligibility Breast cancer screening policy BC Cancer Agency
Alberta Recommendation for high risk populations

Calgary Breast Health Program
Breast cancer screening resources for healthcare providers – Alberta Health Services
Saskatchewan   Saskatchewan Screening Program for Breast Cancer (SPBC) Saskatchewan Cancer Agency
Manitoba Winnipeg Regional Health Authority (WRHA) Breast Health Centre BreastCheck

BreastCheck guidelines
Cancer Care Manitoba
Ontario Ontario Breast Screening Program (OBSP) for high risk women Ontario Breast Screening Program (OBSP) for average risk women Cancer Care Ontario
Quebec   Québec Breast Cancer Screening Program | Le Programme québécois de dépistage du cancer du sein (PQDCS) Santé et Services Sociaux Québec
New Brunswick   New Brunswick Breast Cancer Screening Program New Brunswick Cancer Network (NBCN) is a branch of the Department of Health
Nova Scotia Breast MRI Guidelines including high risk eligibility Nova Scotia Breast Screening Program Nova Scotia Department of Health and Wellness
Prince Edward Island   PEI Provincial Breast Screening Program Health PEI
Newfoundland and Labrador Breast Magnetic Resonance Imaging (MRI) and High Risk Hereditary Breast Cancer (SUMMARY,PDF, November 2012

Breast Magnetic Resonance Imaging (MRI) and High Risk Hereditary Breast Cancer (GUIDELINE, PDF, November 2012)
Breast Screening Program:

Eastern Health
Central Health
Western Health
Cancer Care a program of Eastern Health
Yukon   Yukon Mammography Program at Whitehorse General Hospital Yukon Hospital Corporation
Northwest Territories   Northwest Territories Breast Cancer Screening NWT Health and Social Services
Nunavut     Guidelines under review

How will genetic testing help you and your patient?

If a mutation is identified (a positive test result):

  • Clinical intervention can improve outcomes. (See GECKO Messenger for Screening and Management)
    • Risk-reducing mastectomy lessens the risk of breast cancer by at least 90%
    • Annual magnetic resonance imaging plus mammography increases detection rate for breast cancer
    • Risk-reducing salpingo-oophorectomy decreases the risk of ovarian cancer by at least 80% and, if performed prior to menopause, can reduce the risk of breast cancer by at least 50%
    • Chemoprevention, e.g. tamoxifen, may be considered for some women as a risk-reducing option.
  • Other at-risk family members can be identified and given accurate risk assessments
  • Positive health behaviours can be reinforced


If a mutation is not identified and testing was for a known familial mutation (true negative):

  • Your patient is not considered to be at increased risk of developing hereditary cancer but may still be at increased risk of cancer depending on family history
  • You can provide reassurance to your patient and their children


Table 2. Significant lifetime cancer risks for individuals who have inherited a mutation in the BRCA1 or BRCA2 gene as compared to the general population.

Cancer typeCancer risk in BRCA1 mutation carrierCancer risk in BRCA2 mutation carrierGeneral population cancer risk
Cumulative lifetime invasive breast cancer risk in women (by age 70) 57% 49% ~12%
Cumulative lifetime ovarian cancer risk (by age 70) 40% 18% ~1.3%
Cumulative lifetime breast cancer risk in men (by age 70) increased (controversial) 6-7% 0.1%
Lifetime prostate cancer risk (by age 70) n/a 2-6x increased risk ~14%

NOTE: The literature suggests that there is also an increased lifetime risk for other cancers such as melanoma and pancreatic cancer in BRCA mutation carriers.

For a recent review article on HBOC see US Preventive Services Task Force. Risk assessment, genetic counseling, and genetic testing for BRCA-related cancer. US Preventive Services Task Force recommendation statement. JAMA 2019;322(7):652-665.  

Authors: S Morrison MS CGC, C Cremin MS CGC, E Tomiak MD FRCPC, JE Allanson MD FRCPC and JC Carroll MD CCFP



·           GECKO is an independent not-for-profit program that does not accept support from commercial or non-academic entities.

·           GECKO aims to aid the practicing non-genetics clinician by providing informed resources regarding genetic/genomic conditions, services and technologies that have been developed in a rigorous and evidence-based manner with periodic updating. The content on the GECKO site is for educational purposes only. No resource should be used as a substitute for clinical judgement. GECKO assumes no responsibility or liability resulting from the use of information contained herein.

·           All clinicians using this site are encouraged to consult local genetics clinics, medical geneticists, or specialists for clarification of questions that arise relating to specific patient problems.

·           All patients should seek the advice of their own physician or other qualified clinician regarding any medical questions or conditions.

·           External links are selected and reviewed at the time a page is published. However, GECKO is not responsible for the content of external websites. The inclusion of a link to an external website from GECKO should not be understood to be an endorsement of that website or the site’s owners (or their products/services).

·           We strive to provide accurate, timely, unbiased, and up-to-date information on this site, and make every attempt to ensure the integrity of the site. However, it is possible that the information contained here may contain inaccuracies or errors for which neither GECKO nor its funding agencies assume responsibility.

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