Numerous studies demonstrating positive effects of physical activity in cancer patients have been published over the past decades. Some of these positive effects are reported in multiple high-quality studies – this is called convincing scientific evidence. Other effects are only reported in single studies. This knowledge is not yet confirmed. Little evidence is also available for rare types of cancer or new types of therapies.
What are the effects of physical activity in cancer patients?
Overview of the scientific evidence on exercise and cancer
Here, an overview of the effects of exercise training during and after cancer treatment is given. Evidence is taken from an expert panel publication of the American College of Sports Medicine.
There is convincing evidence that physical activity is safe during and after cancer treatment. This is demonstrated in breast and prostate cancer patients undergoing chemotherapy, radiation and hormone therapy as well as in patients with hematological malignancies undergoing stem cell transplantation. Training is also safe with regard to lymphedema in breast cancer patients. Safety is marked with the highest evidence category A. For other types of cancer, there are only few studies. However, none of these studies raised doubt in patients’ safety and, therefore, the safety appears transferable to other types of cancer.
Cancer patients increase their cardiorespiratory fitness and muscle strength through exercise training. This effect is demonstrated in breast and prostate cancer patients with evidence category A. For patients with hematological malignancies, increases in cardiorespiratory fitness are documented with evidence category B which means that the number of high-quality studies is lower and the results are not consistent. Furthermore, increases in muscle strength are documented with evidence category C in this population, which means that the findings come from studies of lower quality. For other types of cancer there are only few data available, but these data underline positive effects of training on endurance and strength.
In patients with breast cancer, flexibility improves through physical activity (evidence category A). Limited flexibility after surgery is rarely investigated in patients with other types of cancer.
Exercise training counteracts functional limitations and improves functional capacity for activities of daily living. This is demonstrated for breast and prostate cancer patients (evidence category A and B, respectively). There are not enough studies in patients with other types of cancer but the findings in breast cancer patients appear transferable.
Another effect of exercise training is a decrease in body fat mass and an increase in muscle mass. This effect is demonstrated in breast cancer patients undergoing chemotherapy and/or radiation and in prostate cancer patients undergoing hormone therapy (evidence category B). These findings appear transferable to patients with other types of cancer but the body of evidence is too small for a high evidence category.
More and more studies suggest that physical activity prolongs overall and cancer specific survival in patients with breast, colorectal and prostate cancer. However, these findings come from observational studies which are less meaningful compared to training intervention studies. Therefore, the data must be interpreted with great caution and there is not yet an evidence category for effects of physical activity on survival.
Physical activity reduces cancer related fatigue. This effect is demonstrated for prostate cancer patients (evidence category A), breast cancer patients (evidence category B) and patients with hematological malignancies with and without stem cell transplantation (evidence category C and B, respectively). Physical activity is often considered the only effective measure against fatigue. Single studies in patients with other types of cancer show similar results but their number is too small for comprehensive evidence.
Physical activity improves quality of life which is demonstrated for breast and prostate cancer patients (evidence category B) as well as for patients with hematological malignancies (evidence category C). On the other hand side, physical inactivity appears to reduce quality of life. These findings are probably transferable to patients with other types of cancer, but there are not enough studies for a solid statement so far.
Physical activity reduces anxiety and depression in breast cancer patients (evidence category B). Reviews in which studies in patients with various types of cancer types were included also showed a reduction in depression through exercise.
Further positive effects of physical activity were observed in single studies. However, the body of literature is not sufficient for convincing evidence. The positive effects include reduced side effects of chemotherapy and radiation as well as less pain and other symptoms of disease. In addition, single studies found positive effects on the immune system, bone health peripheral neuropathy, tumor cachexia, incontinence and sexual function. And finally, exercise training reduces the risk of other diseases associated with physical inactivity.
The body image improves through physical activity in breast cancer patients (evidence category B). A review including studies in patients with different types of cancer also revealed positive effects on body image.
Single studies suggest further positive effects on the psycho-social level. These include improvements in mood, emotional well-being and self-esteem. Furthermore, sleeping disorders improved through training according to several studies. However, the body of literature is not sufficient for a final evaluation.