AR and neoplasm: The PROPHECY trial evaluated baseline circulating tumor cell (CTC) AR-V7 among 118 patients prior to initiation of enzalutamide or abiraterone and found that the presence of CTC AR-V7 is associated with shorter PFS and OS, and only 0–11% of patients showed a PSA response compared to 26–28% in AR-V7 negative patients based on the assay used [28,29].