Androgen deprivation therapy (ADT) forms the cornerstone of treatment in locally advanced and metastatic prostate cancer (PCa). Since the growth hormone-insulin-like growth factor (GH-IGF-1) axis has been implicated in prostate tumorigenesis, we aimed to evaluate the association between IGF-1 and its binding proteins on outcomes in men with metastatic PCa treated with ADT, with or without docetaxel (D). We analyzed serum samples for IGF-1 and its family proteins from baseline, 6 months post-randomization, and at the time of progression in men enrolled to receive ADT +/- D in the phase 3 CHAARTED trial. The key outcomes were time to the development of castrate-resistant prostate cancer and overall survival (OS). About 560 patients had samples available for analysis. At 6 months, significant increases in IGF-BP1 (mean Δ+27.4%, P = 0.033), IGF-BP3 (mean Δ+10.3%, P < 0.001), and IGF-BP4 (mean Δ+31.1%, P < 0.001) were seen in the ADT + D group, while the ADT group showed an increase in IGF-BP3 (mean Δ+5.5%, P = 0.015). A higher IGF-1:IGF-BP1 ratio at baseline and after 6 months was associated with improved OS in both the ADT (baseline: hazard ratio (HR) = 0.77, P = 0.026; 6 months: HR = 0.83, P = 0.036) and ADT + D groups (baseline: HR = 0.78, P = 0.04; 6 months: HR = 0.81, P = 0.018). Patients with a log10IGF-1:IGF-BP1 ratio >1.3 at baseline had improved OS when meta-analyzed with data from a prior cohort (HR = 0.71). A higher baseline and 6-month IGF-1:IGF-BP1 ratio was associated with better OS. Further exploration of the IGF-1 axis will be important to assess its role as a predictive biomarker and to target this axis in therapeutic trials.
Keywords: IGF-1; IGF-BP1; androgen deprivation therapy; chemotherapy; metabolism.