Effects of aromatase complex selective inhibition on insulin-like growth factor 1 and insulin-like growth factor binding protein 3 circulating levels in breast cancer

The aim of our study is to evaluate insulin-like growth factor (IGF) and IGF binding protein (IGFBP)-3 circulating levels in postmenopausal women treated with type I aromatase inhibitor formestane for breast cancer. Sixty-three patients at their first relapse entered the trial and were randomly given formestane at 250 mg or 500 mg i.m. fortnightly. Effects of the endocrine treatment on IGF-1 and IGFBP-3 were measured before and during therapy at scheduled times. IGF-1 and IGFBP-3 seems to slightly increase in both the dose groups, but only IGFBP-3 levels showed statistically significant fluctuation (baseline vs 4 weeks, p=0.01925; baseline vs 10 weeks, p=0.04537). These modifications are unlikely to be related to clinical status because they were observed both in responsive and unresponsive patients. This report demonstrates that hormonal treatments for breast cancer (particularly, aromatase inhibitor administration) can modify growth factor disposition to tumour.