Although there is no absolute consensus on the criteria of high-risk and low-risk PCa, Gleason score, cancer stage, percent of biopsy core with cancer, and PSA (prostate-specific antigen) have been used in clinical practice and many studies for PCa risk stratification, sometimes with additional consideration such as PSA density (Selvadurai et al., 2013; Klotz et al., 2015; Tosoian et al., 2016; Jones et al., 2018). Here, KLK3 is linked to cancer.