Androgen receptor (AR) splice variant V7 may predict response to new generation androgen signaling inhibitors (i.e. Abiraterone acetate and Enzalutamide), as well as taxane-based chemotherapy.1-2 Although it has been detected in circulating tumor cells (CTCs) of castration-resistant prostate cancer (CRPC) patients, the implementation of CTC-based AR-V7 determination for treatment selection in CRPC into current clinical practice is limited. Indeed, CTCs are usually abundant only in patients with high metastatic tumor burden, and sample processing can require specialized equipment.3