Background: Insulin-like growth factors (IGF's) play a crucial role in
controlling cancer cell proliferation, differentiation and apoptosis.
Exercise has been postulated as an effective intervention in improving
cancer-related outcomes and survival, although its effects on IGF's are
not well understood. This meta-analysis aimed to determine the effects
of exercise in modulating IGF's system in breast cancer survivors.
Methods: Databases of PuMed, EMBASE, Cochrane Central Register of
Controlled Trials, EMBASE, ClinicalTrials. gov, SPORTDiscus, LILACS and
Scopus were systematically searched up to November 2014. Effect
estimates were calculated through a random-effects model of
meta-analysis according to the DerSimonian and Laird method.
Heterogeneity was evaluated with the I-2 test. Risk of bias and
methodological quality were evaluated using the PEDro score.
Results: Five randomized controlled trials (n = 235) were included. Most
women were post-menopausal. High-quality and low risk of bias were found
(mean PEDro score = 6.2 +/- 1). Exercise resulted in significant
improvements on IGF-I, IGF-II, IGFBP-I, IGFBP-3, Insulin and Insulin
resistance (P <0.05). Non-significant differences were found for
Glucose. Aerobic exercise improved IGF-I, IGFBP-3 and Insulin. No
evidence of publication bias was detected by Egger's test (p = 0.12).
Conclusions: Exercise improved IGF's in breast cancer survivors. These
findings provide novel insight regarding the molecular effects of
exercise on tumoral microenvironment, apoptosis and survival in breast