Currently, initial treatment choice is based exclusively on clinical variables (mainly PSA, clinical T-stage (cT), and the biopsy Gleason Score (GS) [8]), but these are suboptimal, leading to the overtreatment of many clinically insignificant prostate cancers as well as the delayed/suboptimal treatment of aggressive prostate cancers [9,10]. Here, KLK3 is linked to Familial prostate cancer.