What About Breast Cancer?

Breast cancer is a common type of cancer. In Canada, 1 in 9 women (12%) are diagnosed with breast cancer in their lifetime.  Generally, 5-10% of breast cancers are thought to be hereditary. Most often, hereditary breast cancer is caused by inherited mutations in the BRCA1 and BRCA2 genes. This means that women with a family history of ovarian cancer may also have an increased risk to develop breast cancer.


Clues that a breast cancer is hereditary are:

  • Early age at diagnosis, particularly before age 35
  • A specific type of breast cancer called triple negative breast cancer
  • Family history of breast cancer, especially premenopausal breast cancer
  • Family history of ovarian cancer

A woman with a BRCA1 or BRCA2 gene mutation may have up to a 70% chance of developing breast cancer in her lifetime. Those with a previous diagnosis of breast cancer also have an increased risk of developing a second breast cancer. Unlike ovarian cancer screening, breast cancer screening may find breast cancers at earlier stages. For women at high risk to develop breast cancer, annual screening involves a mammogram and a breast MRI. 


Without an inherited gene mutation, a family history of breast cancer may still increase a woman’s risk of developing breast cancer. For this reason, the Ontario Breast Cancer Screening Program (OBSP)’s high risk screening program coordinates annual mammograms and breast MRIs to women in Ontario, between ages 30-69, whose breast cancer risk is estimated to be more than 25%.  As part of this study, a risk assessment will be completed for all women, regardless of their genetic testing results.