Clinical significance of AR amplification from CF DNA among Japanese castration-resistant prostate cancer patients.

Abstract

314 Background: We study the prognostic ability of androgen receptor amplification (AR amp) from cf DNA in Japanese castration-resistant prostate cancer (CRPC) patients. Methods: Multiple sets of serums were obtained from 38 castration-resistant prostate cancer patient at Chiba University hospital. Serum cfDNA was purified using a cobas cfDNA Sample Preparation Kit. AR copy number was measured using the QX100 Droplet Digital PCR System. Factors associated with progression-free survival (PFS) and Overall Survival (OS) were statistically studied. Results: The number of patients received Enzalutamide (Enza)/Abiraterone (Abi)/Docetaxel (Doc) were 33/25/11. Regarding PFS, the presence of AR amplification, Bone Scan Index (BSI), PSA was significant factors on univariate analysis. On multivariate analysis, AR amplification was an independent prognostic factor (HR. 8.9, p=0.003). Regarding OS, PSA and AR amp was significant factors. On multivariate analysis, AR amp (HR 4.2, p=0.028) was an independent prognostic factor. AR amp was related to the young age, high bone metastasis, high PSA, while no association was identified related the visceral metastasis. Overall, the presence of AR amp was negatively related to the initial ADT periods (r=-0.28). In contrary, among primary resistance cases (initial treatment periods <1 year), AR amp positively related to the treatment periods (r=0.31). Higher nadir testosterone (>15 ng/dL) was related to the higher AR amp (p=0.0169). AR amp was related to the treatment resistance in Enza (p=0.0216), while no relation was observed in Abi or Doc. Conclusions: AR amp significantly correlated with the poor prognosis. Higher serum testosterone level may predict the presence of AR amp in cf DNA. [Table: see text]