Abstract: For this 2015 update we included a total of 32 studies with 2626 randomised women, 8 studies from the original search and 24 studies from the updated search. We found evidence that physical exercise during adjuvant treatment for breast cancer probably improves physical fitness (SMD 0.42, 95% confidence interval (CI) 0.25 to 0.59; 15 studies; 1310 women; moderate-quality evidence) and slightly reduces fatigue (SMD -0.28, 95% CI -0.41 to -0.16; 19 studies; 1698 women; moderate-quality evidence). Exercise may lead to little or no improvement in health-related quality of life (MD 1.10, 95% CI -5.28 to 7.48; 1 study; 68 women; low-quality evidence), a slight improvement in cancer site-specific quality of life (MD 4.24, 95% CI -1.81 to 10.29; 4 studies; 262 women; low-quality evidence), and an improvement in cognitive function (MD -11.55, 95% CI -22.06 to -1.05; 2 studies; 213 women; low-quality evidence). Exercise probably leads to little or no difference in cancer-specific quality of life (SMD 0.12, 95% CI 0.00 to 0.25; 12 studies; 1012 women; moderate-quality evidence) and little or no difference in depression (SMD -0.15, 95% CI -0.30 to 0.01; 5 studies; 674 women; moderate-quality evidence). Evidence for other outcomes ranged from low to moderate quality. Seven trials reported a very small number of adverse events. Exercise during adjuvant treatment for breast cancer can be regarded as a supportive self care intervention that probably results in less fatigue, improved physical fitness, and little or no difference in cancer-specific quality of life and depression. Exercise may also slightly improve cancer site-specific quality of life and cognitive function, while it may result in little or no difference in health-related quality of life. This review is based on trials with a considerable degree of clinical heterogeneity regarding adjuvant cancer treatments and exercise interventions. Due to the difficulty of blinding exercise trials, all included trials were at high risk for performance bias. Furthermore, the majority of trials were at high risk for detection bias, largely due to most outcomes being self reported. The findings of the updated review have enabled us to make a more precise conclusion that both aerobic and resistance exercise can be regarded as beneficial for individuals with adjuvant therapy-related side effects. Further research is required to determine the optimal type, intensity, and timing of an exercise intervention. Furthermore, long-term evaluation is required due to possible long-term side effects of adjuvant treatment.

Plain-language summary: 32 studies involving 2626 women. The included studies were published up through March 2015. Not all studies considered all of these potential side effects. Combining the results of these studies suggests that physical exercise probably improves physical fitness and slightly lessens fatigue. These studies also suggest that physical exercise probably results in little or no improvement in cancer-specific quality of life and depression. Exercise may improve mental function and slightly improve cancer site-specific quality of life, although the quality of the evidence was low for both of these outcomes. It may result in little or no improvement in health-related quality of life, however the quality of evidence was low for this outcome. The quality of evidence may have been low because many of the studies did not have enough participants to observe small differences and because results may be biased due to people assessing the outcomes knowing which participants were in the control group. Importantly, physical exercise did not harm most women. Very few women experienced discomfort or pain in their arms or legs. It appears that exercise during cancer treatment can help lessen fatigue and improve physical fitness. It probably results in little or no improvement in cancer-specific quality of life and depression. It is unknown whether it helps for other side effects. At least nine current studies will help to answer the question if and how much exercise helps with the mentioned side effects and other side effects.