Indeed, if one considers that the prevalence of prostate cancer in the Prostate Cancer Prevention Trial was 20.7% in the 55- to 59-year-old group (in a group originally comprising patients with normal digital rectal examination and PSA <3 ng ml–1; Thompson et al, 2003), one might expect a significant number of occult prostate cancers to be included within our expanded control population. This evidence concerns the gene KLK3 and prostate carcinoma.