Grant: Operating Grant

Physical activity reduces the risk of breast cancer by 25-30% when comparing the most to least active women. We conducted the Breast Cancer and Exercise Trial in Alberta (BETA) in Calgary and Edmonton between 2010 and 2014 to study how exercise reduces breast cancer risk. BETA was a year-long exercise intervention in 400 postmenopausal women aged 50-74 years who were healthy but inactive. It is the largest ever trial of its kind that has been conducted in the world, had excellent adherence to the exercise intervention and very few study drop outs (96% retention). The study participants were randomly assigned to do either 150 or 300 minutes per week of aerobic exercise: 5 days per week of which 3 days weekly were supervised and 2 were home-based sessions. Each woman had several measurements of her body taken at the beginning, 12 and 24 month time points including providing a fasting blood sample. We have previously investigated how these two levels of exercise influenced biomarkers that could explain how exercise reduces breast cancer risk. We examined the changes in levels of sex hormones, insulin resistance, inflammation, body composition and body fat. We are now interested in understanding if other biological pathways may also be important. With bloods previously stored and frozen from our study participants, we will examine how exercise has influenced markers of oxidation and chronic stress as well as markers of DNA damage and repair (i.e. telomere length and DNA methylation). The proposed study is the first to examine how different doses of exercise influence these biomarkers within the context of a year-long controlled exercise trial in postmenopausal women. Since all of the bloods have already been collected, this study leverages an existing resource and is therefore very cost efficient. This research will provide valuable new information to complement what has already been learned from BETA on how different amounts of exercise reduce breast cancer risk.