The most widely adopted definition of nmCRPC, derived from the recommendations of the Prostate Cancer Working Group 3, is a 25% increase from the PSA nadir (considering an initial value of ≥1 ng/mL) in men with castrate levels of serum testosterone, with a minimum rise of 2 ng/mL, which must be confirmed with a second value obtained 1–3 weeks later without evidence of metastases [11]. This evidence concerns the gene KLK3 and prostate carcinoma.