Being physically active can reduce the risk of cancer and aids survival after diagnosis
By Christine M. Friedenreich
Being active and physically fit are becoming established means for reducing the risk of developing cancer and improving survival after cancer. More than 200 studies have been published in the past 20 years that have clearly shown how higher levels of physical activity reduces the risk of colon, breast and endometrial (uterine) cancers by 25 to 30 per cent and lung, prostate and ovarian cancers by 10 to 20 per cent.
In the past three years, nearly 20 studies have found that physical activity done either before or after cancer diagnosis reduced the risk of death from breast, colon and prostate cancer by 30 per cent or more. Although it is not entirely clear exactly what type and amount of exercise is needed to reduce cancer risk and improve survival, thus far the recommendations are to do at least 150 minutes of moderate or 75 minutes of vigorous intensity activity per week.
Ongoing research is examining how much activity is needed to reduce cancer risk and improve survival. In Alberta, we have conducted several studies to determine how physical activity influences cancer risk, as well as how exercise improves quality of life and survival after cancer. One such study is the Breast Cancer and Exercise Trial in Alberta (BETA trial). In this trial, we are randomly allocating nearly 400 women aged 50-74 years of age either 150 or 300 minutes per week of aerobic exercise. Each woman is on the trial for one year, with the amount of exercise gradually increased over the first three months and then maintained for the last nine months. Three sessions per week are supervised and two are home-based. The BETA trial examines how aerobic exercise influences several biomarkers related to breast cancer risk.
A previous trial (Alberta Physical Activity and Breast Cancer Prevention Trial — ALPHA) found women who were doing almost 200 minutes per week of exercise experienced several benefits related to breast cancer risk. These included lower levels of body fat, female sex hormones, insulin and insulin resistance, leptin, and inflammation. The BETA trial is determining if more exercise is even better for improving these intermediate biomarkers for breast cancer.
Very recently, researchers have begun examining how sedentary behaviour is related to a higher risk of several chronic diseases, including cancer. About 60 per cent of most people’s time is spent in sedentary activity (e.g. driving to work, sitting at work, eating meals, watching television) and only about five per cent is spent doing moderately vigorous activity such as exercise.
Spending too much time sitting has several negative health consequences including higher levels of body fat, cholesterol and blood pressure that are well-established risk factors for cardiovascular diseases, stroke, diabetes and cancer.
Even small breaks in sedentary behaviour of a few minutes have been shown to have beneficial effects on these biomarkers. Hence, there is more emphasis on how to decrease sedentary time.
Some suggestions include walking or cycling for transportation, taking breaks for walking or exercise, having standing meetings, using a desk that allows a change in height to permit working while standing (e.g. while doing e-mail on a computer, during telephone calls), and walking down the hall to speak with a work colleague rather than sending an e-mail.
In 2009, the National Cancer Institute of Canada – Clinical Trials Group initiated the first exercise intervention trial of cancer survival. The Colon Health and Life Long Exercise (CHALLENGE) trial is currently enrolling almost 1,000 colon cancer survivors in Canada and Australia in a three-year exercise study that will determine if regular exercise after colon cancer treatment improves survival. Half of the colon cancer survivors will do a combination of supervised and home-based exercise and half will receive health education materials. Previous observational research has shown being physically active improves survival after colon cancer.
There is strong, consistent evidence that regular, moderate to vigorous intensity physical activity decreases the risk of several cancers and also improves cancer survival. Although sustained, lifelong activity confers the most benefit, even activity begun later in life has been shown to decrease risk.
Fitness study tracks breast cancer patients
Over the next five years, we will enrol 1,500 newly diagnosed breast cancer patients in the Alberta Moving Beyond Breast Cancer (AMBER) cohort study and measure their activity and fitness levels at the time of their diagnosis and then again one, three and five years after diagnosis. All of these women will be followed for an additional five years to assess if they have a progression, recurrence or die because of their cancer.
The women in this study will be asked to complete questionnaires about their health and well-being, provide blood samples, complete a full set of fitness tests, and have their body composition assessed with a DXA scan. The participants will be provided the results of these fitness tests. This study will determine if being physically active and fit improves a woman’s chance of survival after breast cancer. More information is available at amberstudy.com.
— Christine Friedenreich
Christine M. Friedenreich, Ph.D, is a senior research scientist at Alberta Health Services-Cancer Care, an adjunct professor at the University of Calgary and an Alberta Innovates–Health Solutions Senior Scholar.