Current Projects

Examining the Etiology of Young-onset Breast Cancer in the Canadian Partnership for Tomorrow Project

Breast cancer remains the most commonly diagnosed cancer among Canadian women. There has been a marked rise in breast cancer incidence in younger women over the past 25 years. The disease burden of breast cancer disproportionately affects younger women (<50 years of age) since these cancers often occur outside of screening programs, resulting in advanced stage at diagnosis and poorer survival rates. The diagnosis of young-onset breast cancer also presents several unique challenges, including fertility concerns and reduced quality of life due to treatment-induced premature menopause. 

While mutations in the BRCA1 and BRCA2 genes increase the risk of developing breast cancer, only a small number of breast cancers (~5-10%) diagnosed among young women are attributable to these mutations, suggesting other unknown genetic or lifestyle factors may contribute to the development of young-onset breast cancer. Despite the clear need, comparatively few studies have examined breast cancer risk factors among young women.

The limited number of studies that have included young-onset breast cancer cases have presented conflicting results, predominantly using reproductive risk factors. In particular, the association between increased body weight and young-onset breast cancer risk requires clarification, with paradoxical inverse associations reported and a conflicted evidence base. Furthermore, the mechanisms explaining the underlying pathways in these associations remain unclear. 

This project will combine three of the five cohorts involved in the Canadian Partnership for Tomorrow Project that have linked their cohorts to provincial cancer registry databases: Alberta’s Tomorrow Project (ATP); BC Generations Project(BCGP); and the Ontario Health Study (OHS) to investigate risk factors for young-onset breast cancers. A pilot study characterizing mutational signatures in young-onset breast cancer cases using exome sequencing from the ATP will also be initiated. 

The overall aim of this project is to examine the individual and combined effects of family history, lifestyle and reproductive factors, and anthropometric measurements on young-onset breast cancer risk. The specific objectives are to: 

• Examine the impact of lifestyle, environmental, reproductive, family/medical history and breast cancer screening factors on breast cancer risk in young women (<50 years old). 
• Conduct a pilot exome sequencing study using linked tumor samples to examine mutational signatures in young-onset breast cancers and the mechanisms through which obesity and other factors impact the etiology of young-onset breast cancer. 

The results generated from this project will improve understanding of breast cancer etiology in this expanding population of young-onset cases. This understanding could eventually lead to improved primary prevention and secondary