Graf RP, et al. - Experts sought to illustrate the clinical advantage of the nuclear-localized androgen receptor splice variant 7 (AR-V7) test for men with progressing metastatic castration-resistant prostate cancer (mCRPC) at the second line of therapy or greater to inform the choice of an androgen receptor signaling inhibitor (ARSI) or a taxane. A cross-sectional cohort was included to include a sum of 193 unique individuals with progressing mCRPC from whom 255 samples were drawn at the time of the second-line or later treatment decision who then received an ARSI or taxane, with up to 3 yr of additional follow-up Circulating tumor cells (CTCs) were identified from blood samples and tested for AR-V7. The physician propensity was assessed for choosing an ARSI or taxane-based on patient prognosis. The evidence suggested that the advantage of the nuclear-localized AR-V7 CTC test to inform treatment choice can enhance patient outcomes relative to decisions based solely on standard-of-care measures.