AR and neoplasm: However, the emergence of the AR splicing variant ARv7 may represent the key factor for the development of Enz-resistance as recent clinical studies from CRPC patients demonstrated that 39% of metastatic CRPC patients treated with Enz had detectable ARv7 in their circulating tumor cells8, and these ARv7 positive patients had lower PSA response rates than ARv7 negative patients with shorter PSA progression–free survival (median, 1.4 months vs. 6.0 months), suggesting CRPC patients with ARv7 might have poor response to Enz treatment, and Enz treatment might enhance ARv7 expression8.