Current status of circulating tumor cell androgen receptor splice variant-7 in metastatic castration-resistant prostate cancer

In castration resistant prostate cancer (CRPC), the androgen receptor (AR) pathway remains activated through upregulation of AR, mutation, and paracrine/autocrine androgen synthesis (1). Clinical significance of AR variant 7 (AR-V7) in circulating tumor cells (CTCs) was first reported by Antonarakis et al., which demonstrated a strong association with abiraterone and enzalutamide treatment resistance (2). On the other hand, due to the naïve nature of CTCs, detection of AR-V7 status by CTCs had some limitations includes reproducibility of AR-V7 positivity, heterogeneity between institutions. Furthermore, previous studies rarely attempt to compare the AR-V7 expression between tissue and CTCs. There have been several iss