Dr Friedenreich is a cancer epidemiologist with the Department of Cancer epidemiology and Prevention Research (CEPR) of Cancer Control Alberta, Alberta Health Services and an Adjunct Professor in the Faculties of Medicine and Kinesiology of the University of Calgary. She holds a health Senior Scholar career award from Alberta Innovates-Health Solutions and in 2012 was named the Alberta Cancer Foundation's Weekend to end Women's Cancers Breast Cancer Chair at the University of Calgary. Dr Friedenreich is the Scientific Director for CePR and the Division Head for the Division of Preventive Oncology, Department of Oncology, Faculty of Medicine, University of Calgary. Dr Friedenreich completed her doctorate in epidemiology at the university of Toronto in 1990 and postdoctoral work at the International Agency for Research on Cancer (IARC) in Lyon, France and at the university of Calgary between 1990 and 1994. In 2004-5, Dr Friedenreich was a Visiting Scientist at IARC. In 2013, Dr Friedenreich was a co-recipient of the Canadian Cancer Society's O. Harold Warwick Prize. Dr Friedenreich's research is focused on understanding the role of physical activity in reducing the risk of developing cancer and in improving quality of life and survival after cancer diagnosis. She has conducted over 35 observational epidemiologic and randomized controlled intervention trials in this area.

ABSTRACT

Substantial evidence exists for a beneficial effect of physical activity across the cancer continuum.  To date, nearly 400 studies have examined some aspect of physical activity and how it is related to cancer risk and about 40 studies have investigated the role of activity in cancer survival. There is “convincing” evidence that physical activity reduces the risk of breast, colon and endometrial cancers. In total, 80 out of 111 studies in breast cancer have demonstrated, on average, about a 20-25% risk reduction when comparing the least to most physically active participants in these studies. In addition, evidence of a dose-response effect of decreasing risk with increasing activity levels exists in 53 of 88 studies on breast cancer. For colon cancer, 79 out of 100 studies have found reduced risks of about 25-30% and a dose response in 43 of 56 studies. The evidence for endometrial cancer is also consistent with 27 out of 32 studies observing 25-30% decreased risks and a dose-response in 14 out 23 studies.  Physical activity done before and after diagnosis also appears to reduce the risk of recurrences and deaths associated with breast, colon and prostate cancers with reductions in cancer-specific mortality around 25-30%. Randomized controlled exercise intervention trials have found that the main mechanisms involved in the association between physical activity and cancer risk and survival are effects on adiposity, endogenous sex steroids, insulin resistance and inflammation. Other possible pathways involve effects on genomic instability, DNA methylation and oxidative stress.  On-going cohort and randomized controlled trials are specifically addressing some of the limitations in previous studies by incorporating objective measurements of activity, sedentary behaviour, health related fitness. Future priorities in this field include more molecular epidemiologic studies that target the underlying biologic pathways as well phase III randomized controlled trials of exercise in cancer survivors.