Prior Long Response to Androgen Deprivation Predicts Response to Next-generation Androgen Receptor Axis Targeted Drugs in Castration Resistant Prostate Cancer

Background: There is an urgent need for qualified predictive biomarkers of sensitivity for the treatments used in patients with castration-resistant prostate cancer (CRPC). We attempted to identify ready-to-use clinical predictors of improved outcome in metastatic CRPC (mCRPC) patients treated with next generation androgen receptor (AR) axis targeted drugs.

Patients And Methods: We reviewed a cohort of patients who received AR axis targeted drugs for CRPC at two major French cancer centres. The predictive role of several clinical, biological and radiological parameters on progression-free survival (PFS) was studied.

Results: The study cohort consisted of 173 patients. Median duration of response to initial androgen deprivation therapy (ADT) (time to castration resistance, TTCRPC) was 17.8 months. The 50% prostate-specific antigen (PSA) response rate to AR axis targeted drugs was 16% (95% confidence interval (CI): 6-27) and 41% (95% CI: 30-47) in patients with TTCRPC of under and over 12 months respectively (p=0.005). Median PFS was 2.8 months (95% CI: 2.1-3.9) and 5.8 (95% CI: 4.6-7.8; HR: 0.58, p=0.002). In patients treated with post-docetaxel enzalutamide (n=57), median PFS was 2.8 months and 8.6 months, (Hazard ratio (HR)=3.1; 95% CI: 1.6-5.8, p=0.0016) according to TTCRPC, whereas no difference was observed in placebo-treated patients (n=27). The 50% PSA response rate to enzalutamide was 8% (95% CI: 0-38) and 58% (95% CI: 42-73) in patients with a TTCRPC of under and over 12 months respectively (p<0.001).

Conclusion: The previous duration of response to ADT is a predictor of sensitivity to next generation AR axis targeted drugs in patients with mCRPC.