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 Alberta Physical Activity and Breast Cancer Prevention Trial (ALPHA Trial) in Calgary and Edmonton between 2003-2007 to study how exercise reduces breast cancer risk. The ALPHA Trial was a year-long exercise intervention in 320 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. The study participants were randomly assigned to do either aerobic exercise or to maintain their regular lifestyle of no exercise. The exercise group did 5 days per week of aerobic activity of at least 45 minutes (3 days weekly were supervised and 2 were home-based sessions). Each woman had several measurements of her body taken at the beginning, six and 12 month time points including providing a fasting blood sample. We have previously reported that the exercisers had reduced levels of sex hormones, insulin resistance, inflammation, and all measures of 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 as well as markers of DNA damage and repair (i.e telomere length and DNA methylation). This study is the first to examine several of these biomarkers within the context of a year-long controlled exercise trial in postmenopausal and will provide new insights on how exercise may decrease cancer risk. Since all of the bloods have already been collected, this study leverages an existing resource and is consequently very cost efficient. This research will provide valuable new information to complement what has already been learned from the ALPHA Trial on how exercise reduces breast cancer risk.