IGF1 and prostate cancer: The present study had a robust sample size (n = 793) and clearly demonstrated a lower risk of high surgical GS in patients with high serum IGF‐1 level (highest vs lowest quartile, OR = 0.494; Ptrend = 0.006; Table 3), whereas the risk of prostate cancer itself was positively associated with serum IGF‐1 level (OR = 3.35, Ptrend < 0.001; Table 1).