Abstract
Background: Physical exercise is suspected to reduce cancer risk and mortality. So far, little is known about the underlying mechanisms. Although limited, murine models represent a promising attempt in order to gain knowledge in this field.Objective: A systematic review and meta-analysis examining various treatment protocols was conducted in order to determine the impact of exercise on tumor growth in rodents.Methods: PubMed, Google scholar and System for information on Gray literature in Europe were screened from inception to October 2017. Risk of bias within individual studies was assessed using the Office of Health Assessment and Translation risk of bias rating tool for human and animal trials. The effect of exercise on tumor growth over and above non-exercise control was pooled using random-effects model. Subgroup analyses were conducted to identify potential moderators.Results: The quality of the included 17 articles ranged between “probably low” and “high risk of bias.” A significant reduction in tumor growth in exercising animals compared to controls was detected (Hedges' g = −0.40; 95% CI −0.66 to −0.14, p < 0.01) with between-study heterogeneity (τ2 = 0.217, I2 = 70.28%, p < 0.001). The heterogeneity was partially explained by three moderators representing the in-between group differences of “maximum daily exercise” R2 = 33% (p < 0.01), “type of cancer administration” R2 = 28% (p < 0.05), and “training initiation” R2 = 27% (p < 0.05).Conclusion: This meta-analysis suggests that physical exercise leads to reduction of tumor size in rodents. Since “maximum daily exercise” was found to have at least modest impact on tumor growth, more clinical trials investigating dose-response relationships are needed.
Highlights
RationaleVarious fields of health science progressively incorporated the idea that lifestyle factors, such as physical activity could have a greater impact on the general health status than previously believed
The overall results from this meta-analysis suggest that physical activity positively impacts tumor size in rodents
FaustinoRocha and colleagues linked this phenomenon to enhanced blood perfusion initiated by an over-expression of the vascular endothelial growth factor A (VEGF-A)
Summary
RationaleVarious fields of health science progressively incorporated the idea that lifestyle factors, such as physical activity could have a greater impact on the general health status than previously believed. The interest in physical activity, defined as any bodily movement produced by skeletal muscles that results in energy expenditure [1], was solemnly known to cause positive effects in weight management and reduced risks of suffering from cardiovascular disease, hypertension and type 2 diabetes [2]. Pre- and post- diagnosis physical activity is further associated with reduced cancer-specific and overall mortality in patients suffering from colorectal-, breast-, and prostate cancer [6,7,8]. Besides maintenance or improvements in physical capacity, exercise interventions have proven to reduce frequently observed side effects of cancer diseases and their medical treatments such as fatigue, polyneuropathies, depressions, lymphedema, etc. Physical exercise is suspected to reduce cancer risk and mortality. Murine models represent a promising attempt in order to gain knowledge in this field
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