Serum insulin to predict time to castration-resistant progression and overall survival in metastatic androgen-dependent prostate cancer (mADPCa).
e16038 Background: Duration of response to androgen-deprivation therapy (ADT) is highly variable in patients with mADPC and prognostic markers are needed. Insulin resistance and hyperinsulinemia may contribute to prostate cancer progression. We hypothesized that pretreatment serum insulin levels would predict time to castration-resistant progression (PFS) and overall survival (OS). Methods: Sera from men treated on a randomized phase 3 trial of first line ADT vs. ADT plus chemotherapy were retrospectively analyzed using a multiplex ELISA for cytokines and angiogenic factors (CAFs). Univariate and multivariate Cox proportional hazards regression models were used to identify associations between CAFs and PFS/OS. Results: 66 pts were evaluable, 86% Caucasian, median age 72 yrs, median PSA 31.5ng/mL, 77% Gleason score of ≥8, and 53% high volume metastatic disease (HVM). Thirty-five pts received ADT; 31 pts received ADT+chemo. In univariate analysis, higher pretreatment insulin and C-peptide were positively correlated with PFS, whereas higher hepatocyte-growth factor (HGF), osteopontin (OPN) and HVM were negatively correlated with PFS. In multivariate analysis, only higher insulin was associated with longer PFS (HR=0.72, 95%CI 1.32 -0.87; p<0.001), whereas higher HGF and OPN were associated with reduced PFS (HR=1.82, 95%CI 0.59-2.83, p<0.01 and HR=1.81, 95%CI 1.18-2.47, p<0.001, respectively). Higher Insulin and Program Death 1 (PD1) were associated with longer OS on multivariate analysis (HR=0.78 p<0.02 and HR=0.55 p<0.02, respectively), whereas HVM and higher OPN were associated with reduced OS (HR=2.28 p<0.01 and HR=1.60 p<0.02). Using low insulin, high HGF and high OPN as 3 independent risk factors (RF), 3 distinct risk groups could predict PFS: good (zero RF), intermediate (1 or 2 RF) and poor risk (3 RF), with median PFS of 6.90, 1.97, and 0.86 years, respectively (p<0.001). Conclusions: Higher pretreatment insulin was associated with prolonged PFS and OS in men with mADPC treated with ADT. Our data suggest that insulin levels are a biomarker for sensitivity to ADT and highlight the complex interactions between metabolism and PCa progression.