In the past, cancer patients were usually advised to rest and avoid physical effort. However, it is now well established that excessive rest and lack of physical activity may result in severe deconditioning and thus reduced physical functioning. Furthermore, women undergoing chemotherapy or radiation therapy as adjuvant treatment for breast cancer commonly experience debilitating side effects. One of the main side effects of radiation therapy is fatigue; common side effects of chemotherapy are nausea and vomiting, fatigue, weight gain and mood disturbances. These side effects interfere with daily activities such as self-care or return to work. Physical exercise has been reported to improve the underlying conditions in people with a range of chronic diseases.
This review evaluated physical exercise as a means of counteracting several of the side effects that cancer treatments (chemotherapy and radiation therapy) induce. It included nine controlled clinical trials with a total of 452 participants. Results suggest that physical exercise can improve physical function even during cancer treatment. Also, fatigue may be lessened through exercise although there is insufficient evidence to conclude this. There is still not enough evidence about the effect of exercise on outcomes such as mood disturbances, immune function and weight gain. Moreover, there is a lack of evidence for harms of exercise during adjuvant cancer treatment.
Exercise during adjuvant treatment for breast cancer can be regarded as a supportive self-care intervention which results in improved physical fitness and thus the capacity for performing activities of daily life, which may otherwise be impaired due to inactivity during treatment. Improvements in fatigue were ambiguous and there was a lack of evidence for improvement with exercise for other treatment-related side effects. Since exercise interventions (for sedentary participants) require behaviour change, strategies for behaviour change should underpin these interventions. Furthermore, long-term evaluation is required due to possible long-term side effects.
A huge clinical research database on adjuvant cancer treatment has verified improvements in breast cancer outcomes such as recurrence and mortality rates. On the other hand, adjuvant therapy with agents such as hormone therapy, chemotherapy and radiotherapy impacts on quality of life due to substantial short- and long-term side effects.
To assess the effect of aerobic or resistance exercise interventions during adjuvant treatment for breast cancer on treatment-related side effects such as physical deterioration, fatigue, psychosocial distress and physiological, morphological and biological changes.
We searched the Cochrane Breast Cancer Specialised Register (16 July 2004) and the following electronic databases: MEDLINE (1966 to 2004), EMBASE (1988 to 2004), CINAHL (1982 to 2004), SPORTDiscus (1975 to 2004), PsycINFO (1872 to 2003), SIGLE (1880 to 2004), ProQuest Digital Dissertations (1861 to 2004) and Conference Papers Index (1973 to 2004). Furthermore, we screened references in relevant reviews and clinical trials and handsearched relevant journals.
We included randomised and non-randomised controlled trials that examined aerobic or resistance exercise, or both, in women undergoing adjuvant treatment for breast cancer.
Two authors independently extracted data and assessed methodological quality and adequacy of the training stimulus following a set of standardised criteria. Meta-analyses were performed for physical fitness, fatigue and weight gain using a random-effects model.
Nine trials involving 452 women met the inclusion criteria. Meta-analysis for cardiorespiratory fitness (involving 207 participants) suggested that exercise improves cardiorespiratory fitness (SMD 0.66, 95% CI 0.20 to 1.12). Meta-analysis for fatigue (317 participants) found statistically non-significant improvements for participants in the exercise intervention groups compared to control (non-exercising) groups (SMD -0.12, 95% CI -0.37 to 0.13); the same applied for the meta-analysis of weight gain (147 participants) (SMD -1.11, 95% CI -2.44 to 0.22). Evidence for other outcomes remains limited. Adverse effects (lymphedema and shoulder tendonitis) were observed in two trials. The results from non-randomised controlled trials are similar to those of randomised controlled trials and do not appear to produce any bias. This review is based on a small number of trials with a considerable degree of clinical heterogeneity regarding adjuvant cancer treatments and exercise interventions.