A randomized controlled trial of prostate cancer prevention assessed the green tea catechin metabolite plasma level and evaluated the changes in prostate-specific antigen (PSA) in men with an increased risk of prostate cancer (PSA in the range between 2.0–2.974 ng/mL or 2.974–19.95 ng/mL and negative biopsy). Here, KLK3 is linked to Familial prostate cancer.