KLK3 and prostate cancer: Castration-resistant prostate cancer (CRPC), as an advanced stage of prostate cancer progression, is recognized as: castration level testosterone ≤50 ng/dL (or ≤0.50 ng/mL or 1.73 nmol/L) with prostate specific antigen (PSA) progression of at least a 25% increase in PSA from nadir (st ting PSA ≥1.0 ng/ml) or radiological progression (2).