To compensate for the unreliability of PSA, PSA kinetics or prostate biopsies, proPSA (Peter et al. 2001; Mikolajczyk et al. 2001) may be a new candidate biomarker employable at enrollment or AS monitoring, as p2PSA-related indices have high specificity not only for prostate cancer but also for other high-grade and high-volume tumors (Jansen et al. 2010; Catalona et al. 2011; Ito et al. 2012; Guazzoni et al. 2012). This evidence concerns the gene KLK3 and prostate cancer.