Patients who had a biopsy confirmed prostate cancer, with a Gleason score of ≤ 6, ≤ 2 cores positive for prostate cancer, ≤ 50% infiltration in any one core, and PSA density < 0.15ng/mL/mL fulfilled the Epstein criterion for active observation [7]. Here, KLK3 is linked to prostate carcinoma.