Men in the intervention group had smaller tumours, reduced involvement of surgical margins and/or extra‐prostatic tissues with cancer (73% vs. 18%, organ‐confined disease) and less diffuse involvement of the prostate by high‐grade prostatic intraepithelial neoplasia (33% vs. 0%, focal involvement) in comparison with those in the control group. Mean plasma PSA levels were lower in the intervention group compared with the control group. This evidence concerns the gene KLK3 and cancer.