Breast cancer is the most commonly diagnosed cancer among women in Canada. While age remains the strongest risk factor, inherited genetic mutations also play an important role. In approximately five to ten percent of cases, breast cancer is caused by inherited gene mutations. One of the most well-known is BRCA2.

At Breast Cancer Canada, we believe that understanding genetic risk supports earlier detection, more personalized care, and better outcomes for patients and families across Canada.

What is the BRCA2 gene?

BRCA2 (BReast CAncer gene 2) is a gene that helps protect the body from cancer. When it is working properly, it repairs damaged DNA and prevents abnormal cells from growing. When a harmful mutation is present, this repair system does not function as it should, allowing DNA damage to build up and increasing the risk of cancer.

Inherited BRCA2 mutations raise the lifetime risk of breast, ovarian, prostate, pancreatic, and several other cancers. In breast cancer, BRCA2-associated tumours are most often estrogen receptor–positive (ER-positive), though other subtypes can occur.

How does BRCA2 normally protect the body?

Every day, our cells divide and small DNA errors occur. The BRCA2 protein helps repair these errors and prevents damaged cells from continuing to grow. Because of this role, BRCA2 is known as a tumour suppressor gene. When it is not working properly, abnormal cells can grow more easily.

What is a BRCA2 mutation?

Everyone has two copies of the BRCA2 gene, one from each parent. A mutation is a change in the DNA that affects how the gene functions. When a mutation is inherited, it is called a germline mutation and is present in every cell of the body.

Thousands of BRCA2 variants have been identified. Some are harmful, some are harmless, and others are classified as variants of uncertain significance. Inherited BRCA2 mutations are part of hereditary breast and ovarian cancer syndromes, which can affect people of all genders and are associated with higher rates of several cancers.

How does a BRCA2 mutation affect breast cancer risk?

In the general population, about one in eight women in Canada will develop breast cancer. For women with a pathogenic BRCA2 mutation, the lifetime risk is significantly higher.

BRCA2 mutations are also associated with ductal carcinoma in situ (DCIS), a non-invasive form of breast cancer. Most BRCA2-related breast cancers are ER-positive, while a smaller proportion are triple-negative.

People who have already been diagnosed with breast cancer and carry a BRCA2 mutation also face a higher risk of developing cancer in the opposite breast. In men, BRCA2 mutations also significantly increase breast cancer risk.

BRCA2 and ancestry

Some BRCA2 mutations are more common in specific populations because they originated in ancestors and were passed down through generations. These are called founder mutations. They are seen more often in certain communities, including people with Ashkenazi Jewish ancestry, as well as in some Caribbean, European, and African populations.

Understanding these patterns helps improve access to testing and tailored care in Canada’s diverse communities.

BRCA1 vs. BRCA2

BRCA1 and BRCA2 work together to repair DNA, but the cancers they are associated with often differ. BRCA1 mutations are more commonly linked to triple-negative breast cancer, while BRCA2 mutations are more often associated with ER-positive disease.

BRCA1 is also associated with a higher lifetime risk of ovarian cancer compared to BRCA2. In men, BRCA2 mutations are linked to a higher risk of breast cancer than BRCA1.

Genetic testing and counselling in Canada

Genetic testing may be recommended based on personal or family history, ancestry, or known mutations in relatives. Testing is done using a blood or saliva sample.

In Canada, genetic counselling is recommended before and after testing. A genetic counsellor can help interpret results, discuss next steps, and support informed decision-making.

If a pathogenic BRCA2 mutation is found, close family members have a 50 percent chance of carrying the same mutation. Some people choose enhanced screening, while others consider risk-reducing options. These decisions are personal and should be supported by specialized care teams.

How BRCA2 status can guide treatment

For people diagnosed with breast cancer, knowing their BRCA2 status can help guide treatment decisions. PARP inhibitors target cancer cells that rely on backup DNA repair pathways and are now part of treatment for some people with BRCA-related cancers.

New therapies, including antibody-drug conjugates and immunotherapy, are also expanding options for people with aggressive or treatment-resistant disease.

Research driving progress

Across Canada, researchers are working to better understand BRCA2-associated breast cancer and improve care for those at increased genetic risk. This includes improving testing, refining screening, and developing more personalized treatments.

At Breast Cancer Canada, we support research that moves discoveries from the lab into real-world impact for patients.