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In the past, physicians usually advised patients with chronic diseases to rest and avoid physical effort. These recommendations were empirical: as most chronic diseases are associated with functional changes resulting in an impairment of physical performance, exercise in this group of patients may generate fatigue, breathlessness, and tachycardia. Therefore, avoiding physical activity results in less discomfort.
However, in the last few years, scientific evidence has dramatically changed our ideas about exercise for patients with chronic diseases. In the late 1960s, the inclusion of physical activity in rehabilitation programmes for patients who had had myocardial infarction set a milestone and opened up new perspectives for the use of exercise in treatment for chronic diseases. Now, it is a well established fact that excessive rest and lack of physical activity may result in severe deconditioning and thus reduce the functional status and quality of life of the chronically ill. Furthermore, numerous studies have shown that exercise is an effective means for counteracting several of the negative effects that chronic diseases have on physical performance. As a result of this evidence, exercise is actually considered an essential component in the treatment of several illnesses including peripheral vascular disorders, chronic obstructive lung disease, ischaemic myocardial disease, and heart failure. Moreover, the value of exercise for rehabilitation has been widely recognised; indeed, many institutions offer exercise programmes for transplantation recipients and for patients after myocardial infarction or with chronic renal failure. However, until recently, less was known about the feasibility and effects of exercise programmes for cancer patients during and after treatment.
The role of exercise in oncological rehabilitation programmes has thus far been mostly limited to physical treatment addressing specific impairments caused—for example, by amputation or surgery. However, the medical attitude regarding exercise for cancer patients is changing fast. The recent world class performances of athletes who have been treated for cancer have focussed attention on the effects of training on the physical performance of cancer patients. Moreover, recent studies have shown that physical activity may improve both the quality of life and mood and the physical performance of cancer patients during and after treatment.
Regular physical activity has been shown to increase the performance status in breast cancer patients treated with conventional chemotherapy1 and in patients after bone marrow transplantation.2 It has also been shown to reduce psychological distress and fatigue in patients treated with radiotherapy3 and after high dose chemotherapy with peripheral blood stem cell transplantation.4 Furthermore, a reduction of treatment related complications has been observed in cancer patients participating in exercise programmes during cancer treatment.5,6 Finally, preliminary evidence suggests that regular physical activity may improve immune function.7–9 Therefore, exercise could play a potential role as complementary therapy for cancer patients during and after treatment.
However, it is necessary to have more information about the effects and feasibility of exercise programmes for different groups of patients with oncological diseases. Indeed, “cancer” is a common denominator for more than 100 neoplastic diseases, each with a different aetiology, course, and prognosis. Nevertheless, the biology of the same nosological entity may vary considerably in different settings—that is, acute lymphoblastic leukaemia in children and adults. Finally, cancer patients may have a number of specific problems. Chemotherapy can damage bone marrow and thereby impair the production of red blood cells; the resulting anaemia decreases the oxygen transport capacity of the blood. Agents like anthracyclines and cyclophosphamide, and irradiation of the mediastinum, can result in myocardial damage and therefore cause a decrease of cardiac output. Metastatic disease and pleural effusion cause a reduction of total lung capacity; furthermore, changes in the pulmonary architecture due to surgical treatment of primary or metastatic lung cancer or as a sequel to fibrosis after radiotherapy may alter the ventilation:perfusion ratio. Treatment with immunosuppressive agents (for example, high dose corticoids and cyclosporine) can lead to a marked loss of muscle mass and severe myopathy. Furthermore, reduced protein and calorie intake as a consequence of anorexia and nausea, and impaired absorption after gastrointestinal surgery, may lead to a negative nitrogen balance and hence to a catabolic state. Finally, an increase in the concentration of cytokines (IL1, IL6, TNF and IFN-α) resulting from the interaction between the tumour and the host defence system has been associated with muscular waning. All these factors may affect the patient's physical condition and reduce their performance and must thus be carefully considered when designing an exercise programme.
Research about the effects of exercise in the prevention and rehabilitation of cancer and the impact of physical activity on immune function is still at its very beginning. However, we feel that this is going to be one of the most active areas of research in sports medicine in the coming decade. It is certainly time to meet the challenge.