The IVW method provided two positive results: Glutathione S-transferase P (GSTP) was significantly causal in reducing the risk of prostate cancer (OR = 0.962, 95% CI 0.926–0.998, p = 0.038), Glutathione S-transferase omega-1 (GSTO1) also had a significant causal effect on prostate cancer risk reduction (OR = 0.977, 95% CI 0.959–0.995, p = 0.013), neither of which detected heterogeneity, with p values of 0.280 and 0.155 for Cochran’s Q, respectively. This evidence concerns the gene GSTO1 and Familial prostate cancer.