The same conclusion is implied from a meta-analysis of population studies which indicated that circulating measures of IGF-I were related to the risk of prostate cancer in studies where the cancers had been detected as clinically presenting disease but not in studies where the cancers have been detected by prostate-specific antigen (PSA) screening (which are mainly low-risk cancers that never progress to clinical disease) (128). This evidence concerns the gene IGF1 and prostate cancer.