Modulation of insulin-like growth factors following exercise in breast cancer: A meta-analysis of randomized controlled trials

Background: Insulin resistance,Insulin-like growth factor 1 (IGF-1), IGF-2 and IGF binding protein-3 (IGFBP-3) are associated with breast cancer risk, cell growing, apoptosis and other tumoral mechanisms. This study aimed to determine the changes on IGF system following exercise in women with breast cancer. Methods: PRISMA statement and the Cochrane Handbook were followed. We searched MEDLINE, Ovid, EMBASE and Cochrane Central Registers to identify randomized controlled trials published between 1990 and October 2014. Primary outcomes measures were: Insulin resistance,IGF1, IGF-2 and IGFBP-3, whilst waist circumference was evaluated as a measure of body composition. For pooled analysis, mean difference (MD) (p < 0.05 with 95% Confidence interval). Results: Seven studies (n = 321) were included. There was high quality and a low risk of bias. Pooled analyses demonstrated that exercise training resulted in significant changes on IGF-I (MD = -12.9, 95%CI -16.73 to -9.14), IGF-II (MD = -43.4, 95%CI -58.5 to -28.3), IGFBP-3 (MD = -0.61, 95%CI -0.69 to -0.53) and waist circumference (MD = -1.13, 95%CI -2.20 to -0.05). Conversely, non-significant differences were found for Insulin Resistance (MD = 0.64, 95%CI -0.01 to 1.29), Insulin (MD = 0.04, 95%CI -0.24 to 0.34) and Glucose (MD = 0.22, 95%CI -0.32 to 0.78). Reporting bias was not observed. Conclusions: The serum levels of insulin like growth factors (IGF1-IGF2) and IGFBP3 were positively modulated by exercise training in breast cancer survivors, enhancing the physiological basis of exercise in regulating cellular proliferation and other tumoral mechanisms in breast cancer.