In 2009 our team published the Australian guidelines on exercise and physical activity for people with cancer emphasizing the imperative that clinicians should reject the rest strategy. Rather, patients should be physically active most days using a combination of aerobic and resistance training aiming to accumulate 75 to 150 minutes of moderate to vigorous exercise and two or more strength training sessions each week.
This recommendation was based on a growing number of clinical trials in oncology that evaluated exercise training in patients with cancer and was practically identical to the ACSM recommendations for healthy adults. Over the subsequent decade, research in exercise oncology has exponentially expanded. In 2019 we updated the Australian position statement on exercise medicine in cancer management, recommending a more precise exercise prescription tailored to the individual patient.
The benefits of “exercise is medicine” to improve quality of life, physical function, body structure and mental health are well established and accepted. However, there is a separate imperative to understand why there is a relationship between physical activity and cancer-specific survival and recurrence. This has driven a plethora of pre-clinical (bench-top) research investigating a range of potential mechanisms whereby exercise influences tumor biology.
While multiple hypotheses exist to explain the tumor-suppressive mechanisms of exercise, our study published in the February 2022 issue of Medicine & Science in Sports & Exercise® focused on the endocrine function of skeletal muscle. The skeletal muscle system is now recognized as the largest endocrine organ in the body, acutely and chronically producing and releasing a range of molecules, including cytokines, termed “myokines,” originating from muscle tissue. We found that a three-month combined (resistance + aerobic) exercise intervention significantly increased resting serum myokine levels (especially oncostatin M and SPARC) in prostate cancer patients with localized disease. Furthermore, the changes in oncostatin M were positively correlated with changes in lean mass, indicating that training-induced muscle hypertrophy may be a key factor driving serum myokine levels. In addition, we applied serum from the study participants sampled before and after the exercise intervention to prostate cancer cells in vitro. We observed a 21% reduction of prostate cancer cell growth. This exercise training/myokine expression mechanism may partly explain previous epidemiological findings of a positive association between increased physical activity and progression-free survival of prostate cancer patients.
This study provided exciting translational data for optimizing exercise prescription. Previous studies have demonstrated a tumor-suppressive role of altered serological factors after exercise in multiple cancer cell lines, including prostate cancer. However, such studies have limited clinical relevance since the serum applied to the cancer cells was obtained from young, healthy individuals. Our study is the first to report elevated levels of muscle-induced serological factors (myokines) in prostate cancer patients and demonstrated a growth-suppressive effect, providing much higher clinical relevance.
From bench-top to bedside is an important paradigm by which we should investigate current issues in optimizing exercise prescription for cancer patients. Translational research to evaluate different exercise modes, intensities, dosages and timing across cancer types and treatments to elicit tumor-suppressive biological mechanisms is required to determine the optimal exercise prescription for each individual patient with cancer and establish exercise as a cancer medicine.
Jin-Soo Kim, MSc, is a Ph.D. candidate in exercise oncology at the Exercise Medicine Research Institute, Edith Cowan University, Australia. His research interest is the role of exercise-induced biological factors in tumor suppression to enhance the understanding of exercise prescription for optimization. Kim also focuses on developing an experimental design involving exercise that translates pre-clinical outcomes to clinical observations.
Robert U. Newton, PhD, DSc, FACSM, is a professor at the Exercise Medicine Research Institute, Edith Cowan University, Australia. His current research interest is the influence of targeted exercise medicine on tumor biology and exercise medicine for reducing the decline in quality of life, strength, body composition and functional ability in cancer patients.
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