The definition of biochemically recurrent prostate cancer according to American Urological Association/American Society for Radiation Oncology/Society of Urologic Oncology guidelines is a rise in the levels of PSA in the blood after radical treatment like surgery or radiation therapy (PSA of 0.2 ng/mL and a confirmatory value of 0.2 ng/mL or greater after surgery and a nadir of + 2.0 ng/mL after radiation therapy) [44]. Here, KLK3 is linked to prostate cancer.