Background: There is growing evidence that IGF-1 and binding proteins may be involved in prostate cancer promotion and progression.
Patients and methods: IGF-1 and binding proteins (IGFBP-1 and 3) serum levels were measured at baseline and after 3 and 6 months of treatment in a selected group of patients with prostate cancer who were randomly assigned to treatment with bicalutamide, bicalutamide plus anastrozole or bicalutamide plus tamoxifen in a comparative study investigating the role of pharmacological medication in the development of bicalutamide-induced gynecomastia.
Results: Bicalutamide monotherapy does not appear to alter the IGF-1/IGFBP system. In fact, the increase in IGF-1 levels induced by this treatment was paralleled by comparable increases in binding protein (IGFBP-3). No major changes from baseline up to month 6 either in IGF-1 or in IGFBP-1 and 3 were observed in the bicalutamide plus anastrozole arm. The addition of tamoxifen to bicalutamide produced a sharp decrease in IGF-1 levels (p<0.001) coupled with an increase in both IGFBP-1 (p=0.001) and, to a lesser extent, IGFBP-3 (p=0.5).
Conclusions: The concurrent administration of tamoxifen and bicalutamide reduces the synthesis and bioavailability of IGF-1. Moreover, increased binding protein levels might exert antiproliferative and proapoptotic effects on prostate cancer cells, independently of the IGF-1/IGF receptor-mediated survival system. Both effects might have a synergistic inhibitory influence on prostate cancer growth.