Serum levels of insulin-like growth factor-1 and insulin-like growth factor-1 binding proteins after radical prostatectomy

Purpose: Elevated serum levels of insulin-like growth factor-1 (IGF-1) have been consistently shown to be a risk factor for prostate cancer. Alterations in serum IGF-1 binding proteins 1 to 3 have also been associated with prostate cancer risk. A potentially important complication in these studies is that prostate tissue, perhaps especially malignant prostate tissue, may secrete IGF-1 and its binding proteins into serum. In fact, it is possible that altered levels of these proteins observed in subjects at risk for prostate cancer are the result of prostate cancer rather than related to its cause. Materials and Methods: The contribution of prostate cancer to serum levels of IGF-1 and IGF-1 binding proteins was determined by analyzing serum samples from 86 patients with prostate cancer 2 weeks before and 8 weeks after radical prostatectomy. Preoperative and postoperative values for IGF-1 and its 3 major binding proteins were analyzed using univariate and multivariate analysis models. Results: On univariate analysis significant increases and not decreases in IGF-1, IGF binding protein-1 and 3 were observed after prostatectomy. On multivariate analysis a significant post-prostatectomy increase was observed for IGF-1 binding proteins 1 and 3 but the increase in IGF-1 was not significant. Conclusions: Increased levels of IGF-1 and IGF-1 binding proteins were unexpected after prostatectomy. This result makes it extremely unlikely that secretion from the prostate, even if it contains cancer, affects serum levels of these proteins. The implication of these findings is that endocrine production of IGF-1 is a factor in prostate cancer risk. Therefore, strategies to lower serum IGF-1 may be potentially useful.