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Effect of physical activity on disease-free survival in patients receiving adjuvant therapy
Findings from a study published in the Journal of Clinical Oncology demonstrated that among patients who were receiving adjuvant (post-surgical) therapy for stage III colon cancer, those that participated in greater volumes of recreational physical activity, longer durations of light- to moderate-intensity aerobic physical activity, or any vigorous-intensity aerobic physical acitivity experienced significant improvements in disease-free survival.
Disease-free survival rate: the percentage of individuals who are free of the signs and symptoms of cancer after a specified duration of time.
In the study, 2,524 patients were randomly assigned to adjuvant therapy with 3 or 6 months of chemotherapy. The 3-year disease-free survival rate was as follows:
Light-intensity to moderate-intensity activities less than 1 hour per week: 65.7%
Light-intensity to moderate-intensity activities at least 1.5 hours per week: 87.1%
Vigorous-intensity activity less than 1 hour per week: 76%
Vigorous-intensity activity at least 1 hour per week: 86%
Brisk walking less than 1 hour per week: 81.7%
Brisk walking at least 3 hours per week: 88.4%
Muscle-strengthening activity less than 1 hour per week: 81.8%
Muscle-strengthening activity at least 0.5 hour per week: 88.8%
How does physical activity help to improve outcomes?
There are several different mechanisms through which physical activity has been associated with better cancer outcomes. One such mechanism is through regulation of certain hormones such as insulin-like growth factor (IGF). IGF is involved in the growth and survival of tumour cells and promotes a variety of processes that are essential to cancer development. Physical activity also helps to reduce obesity, which is associated with a hormone known as leptin, which has been implicated in the development of wide range of cancers.
Another mechanism that links physical activity to better outcomes is through a reduction in chronic inflammation in the body. Inflammation is a natural process of the body that can favour many of the processes involved in cancer development when it becomes chronic or dysregulated; regular moderate physical activity has been linked to a reduction in chronic inflammation.
Furthermore, physical activity is linked to improved immune functioning. In general, exercising at a moderate to vigorous intensity for 60 minutes or less is optimal for the immune-boosting benefits of exercise. On the other hand, prolonged high intensity training, particularly that which is done without appropriate rest between sessions, can supporess immune function. Exercise also helps to decrease stress, improve sleep (which is when certain components of the immune system become the most active), and positively influence the neurotransmitters in the brain that are responsible for affecting mood and behaviour.
Among patients with stage III colon cancer enrolled in a trial of post-operative treatment, larger amounts of recreational physical activity, longer durations of light-to-moderate intensity aerobic physical activity, or any vigorous intensity aerobic physical activity were associated with the greatest improvements to disease-free survival.