KLK3 and Familial prostate cancer: The Prostate Cancer Prevention Trial included 2950 men that never had a PSA level higher than 4 ng mL−1 over a 7 year period.[12, 13] Each participant underwent a prostate biopsy at the end of the study and 15.2% (449 men) were subsequently diagnosed with PCa.[12] All of these 449 men would have been missed using only the standard 4 ng mL−1 PSA threshold.