Prognostic significance of total plasma cell-free DNA level and androgen receptor amplification in castration-resistant prostate cancer.

PURPOSE To investigate the prognostic significance of total cell-free DNA (cfDNA) level and androgen receptor amplification (AR-amp) in patients with castration-resistant prostate cancer (CRPC). METHODS We retrospectively compared the total cfDNA level and AR-amp in 42 individuals without prostate cancer, 57 patients with localized prostate cancer without androgen-deprivation therapy (ADT), 97 patients with castration-sensitive prostate cancer (CSPC) with ADT, and 97 patients with CRPC. The association of these cfDNA biomarkers on disease status and overall survival was evaluated using Kaplan-Meier analysis and multivariable Cox regression analysis. Finally, a simple risk model was developed including total cfDNA and AR-amp to predict poor prognosis. RESULTS The median total cfDNA level and AR-amp in patients with CRPC was 387 pg/μL and 1.07 copies, respectively. The total cfDNA levels and AR-amp were significantly higher in the patients with CRPC than in individuals without prostate cancer, patients with localized prostate cancer without ADT, and patients with CSPC with ADT. Total cfDNA-high (> 600 pg/μL) and AR-amp-high (> 1.26 copies) were significantly associated with poor overall survival. Multivariable Cox regression analysis showed cfDNA-high and AR-amp-high were significantly associated with poor overall survival in patients with CRPC. We developed a risk model using cfDNA-high (score 1) and AR-amp-high (score 1). The risk score 1-2 was significantly associated with worse overall survival than score 0. CONCLUSION Total cfDNA level and AR-amp are potential biomarkers for poor prognosis in patients with CRPC.