KLK3 and prostate cancer: Approximately 20% to 40% of patients treated with radical prostatectomy (RP) for prostate cancer (PC) will present biochemical recurrence (BCR) defined by an increase of the prostate-specific antigen (PSA) level on two or more consecutive determinations or a persistently rising PSA greater than 0.2 ng/ml after RP (1, 2).