AR and metastatic neoplasm: According to this study the presence of any AR-V was associated with shorter progression-free survival after second-line endocrine treatment compared to patients that did not harbour AR-Vs.34 Furthermore, in another recent investigation AR-GSRs in circulating tumour DNA were shown to associate with primary resistance to enzalutamide or abiraterone also in treatment-naïve CRPC patients with metastatic disease.13