Re: Emmanuel S. Antonarakis, Changxue Lu, Brandon Luber, et al. Clinical Significance of Androgen Receptor Splice Variant-7 mRNA Detection in Circulating Tumor Cells of Men with Metastatic Castration-resistant Prostate Cancer Treated with First- and Second-line Abiraterone and Enzalutamide. J Clin Oncol 2017;35:2149–56