More specifically, the Prostate Cancer Clinical Trials Working Group 3 defined nmCRPC as a progressively rising prostate-specific antigen (PSA) level, namely a 25% PSA increase from nadir (starting PSA ≥ 1.0 ng/mL), with a minimum increase of 2 ng/mL despite a castrate level of testosterone (<50 ng/dL) in the absence of obvious radiologic evidence of metastatic disease on conventional imaging modalities [27]. This evidence concerns the gene KLK3 and metastatic neoplasm.