Expanded Genetic Testing in Women with Young Onset Breast Cancer

Approximately 4% of breast cancers in Canada occur in women before the age of 40 years.  There are only a few known risk factors for young-onset breast cancer are few, and they can only account for a very small proportion of cases. Approximately 15% of all breast cancer cases are estimated to have a hereditary contribution.  To date, the majority of research efforts targeting hereditary breast cancer have focused on BRCA1 and BRCA2, yet these two genes are responsible for only 20% of all inherited breast cancers. At least 23 more known breast and ovarian cancer predisposing (BrOCaP) genes are estimated to be responsible for another 30% of the hereditary breast cancers. Further exploration of the contribution of these genes to young-onset breast cancer is required.  

What is the goal of this sub-project?
The goal of this sub-project is to assess the frequency and predictors of mutations in 25 breast predisposition genes (BrOCaP) in 800 unselected women with breast cancer diagnosed prior to the age of 40 years.  In addition, the investigators will also evaluate the sensitivity of the current genetic testing criteria from all Canadian provinces in detecting important genetic mutations in women with young-onset breast cancer.

What is the design of this sub-project?
Women who consent to participate in the RUBY study will have the opportunity to further consent for this sub-project. Every participant will receive a detailed brochure on genetic testing containing important information about all the genes tested in the study. A genetic counselor will provide genetic test results by telephone and if a woman is identified with a genetic mutation in one of the 25 BrOCaP genes, she will be referred to a local genetic counsellor who will provide follow-up genetic services.

Why is this important?
Our proposed pan-Canadian collaboration, in which 1,200 women with young-onset breast cancer will be recruited, is in a unique position to evaluate the contribution of 25 known breast cancer causing genes in this population of young women. The investigators will be able to assess current genetic testing guidelines to determine if other genes in addition to BRCA1 and BRCA2 should be considered for use in clinical genetic testing for women with young-onset breast cancer. The results of this study and ensuing changes in delivery of cancer genetics services could ultimately have a profound influence on cancer-related mortality in women with young-onset breast cancer and their relatives.

Who are the other investigators on this project?

  • Dr. Steven Narod (Co-Investigator), Women’s College Hospital
  • Dr. Mohammad Akbari (Co-Investigator), Women’s College Hospital


Fully affiliated with

A member of

Council of Academic Hospitals of Ontario (CAHO)