In total, 49 studies were included within the supporting evidence category; 16 of these studies investigated the association between circulating levels of IGF-I (n = 14), IGF-II (n = 2), IGFBP-2 (n = 2) or IGFBP-3 (n = 8) with prostate cancer risk or prostate cancer outcomes such as Gleason grade, TNM stage or PSA-progression free survival. This evidence concerns the gene IGF2 and Familial prostate cancer.