Exercise in survivors of cancer

The benefits of exercise in people with cardiovascular disease are well documented,1 but its effect in people with cancer is less well studied. This is largely because research into the effects of exercise in preventing and recovering from heart attacks and strokes has been studied for much longer. In this week's BMJ, a randomised controlled trial by Mutrie and colleagues assesses the functional and psychological effects of a 12 week exercise programme in women with early stage breast cancer.2 It found no significant difference in the primary outcome of quality of life at 12 weeks as measured by the functional assessment of cancer therapy (FACT-G) questionnaire. However, it did find significant improvements at 12 weeks in secondary outcomes such as the number of metres walked in 12 minutes, the amount of exercise of moderate intensity taken in one week, mobility of the shoulder, and breast cancer specific quality of life. Most of the effects were maintained at six months, and there were no adverse effects. Many studies have focused on the psychological effects of exercise in people with cancer,3 but there is increasing interest in physical outcomes as well.4,5,6 For example, the first randomised controlled trial assessing weight training on mood and quality of life in survivors of breast cancer reported significant improvements in physical global scores (2.1% in the treatment group compared with a 1.2% reduction in the control group). Changes in bench press results significantly correlated with changes in physical global score and psychosocial global score.4 Other studies have shown that exercise may improve quality of life and promote greater acceptance of physical changes associated with treatment for cancer.7,8,9 A recent systematic review of the effects of exercise in people with cancer concluded that although exercise seems to be promising, the included studies had limitations.10 Most studies were small and not randomised, only included women diagnosed with breast cancer, and studied cardiovascular exercise in favour of other forms of exercise such as strength training 10 The trial by Mutrie and colleagues is the first to be carried out in the United Kingdom and has the largest sample size of published exercise trials in breast cancer; however, it too has limitations.10 One such limitation is that it did not look at different subgroups of patients with breast cancer, such as those with genetically linked breast cancer, those with different oestrogen receptor status, premenopausal women, and postmenopausal women. The effectiveness of exercise may well vary within certain subgroups of patients who have had breast cancer, and this needs to be explored in future studies. Clearly these and other outstanding questions warrant further research. For example, can exercise prevent primary malignancy and recurrence of certain cancers? One systematic review of 19 cohort and 29 case controlled studies found an inverse association between physical activity in postmenopausal women and the risk of breast cancer (20-80% reduced risk of breast cancer), compared with a more modest reduction in premenopausal women of 15-20%.11 Other questions include what forms of exercise are the most effective in terms of cardiovascular and strength training recommendations? Could overexercising suppress the immune system and potentially be harmful to women who have had breast cancer? On the basis of the evidence so far, exercise seems to improve the physical and mental health of women diagnosed with breast cancer. However, the optimal time to prescribe exercise and the best intensity, mode, and duration of treatment are unclear. Until further research is completed health professionals can safely recommend exercise incorporating a cardiovascular and strength training component to women with breast cancer.