In recent decades, more than 700 studies involving over 50,000 participants have been published showing the positive effects of physical activity in cancer patients. Numerous effects have been consistently demonstrated by several high-quality studies—this is referred to as convincing scientific evidence. Other effects, however, have only been reported in individual studies.
The following is an overview of the effects of exercise before, during, and after cancer treatment.
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.
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.
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.
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.